For every polynomial of degree 45 with coefficients $1,2,3, \ldots, 46$ (in some order) Tom has listed all its distinct real roots. Then he increased each number in the list by 1 . What is now greater: the amount of positive numbers or the amount of negative numbers? Alexey Glebov

For which maximal $N$ there exists an $N$-digit number with the following property: among any sequence of its consecutive decimal digits some digit is present once only? Alexey Glebov

A square was split into several rectangles so that the centers of rectangles form a convex polygon. a) Is it true for sure that each rectangle adjoins to a side of the square? b) Can the number of rectangles equal 23 ? Alexandr Shapovalov

A convex quadrilateral $A B C D$ with area of $S$ is given. Inside each side of the quadrilateral a point is selected. These points are consecutively linked by segments, so that $A B C D$ is split into a smaller quadrilateral and 4 triangles. Prove that the area of at least one triangle does not exceed $S / 8$. Mikhail Malkin

Chord $D E$ of the circumcircle of the triangle $A B C$ intersects sides $A B$ and $B C$ in points $P$ and $Q$ respectively. Point $P$ lies between $D$ and $Q$. Angle bisectors $D F$ and $E G$ are drawn in triangles $A D P$ and $Q E C$. It turned out that the points $D$, $F, G, E$ are concyclic. Prove that the points $A, P, Q, C$ are concyclic. Azamat Mardanov

A table $2 \times 2024$ is filled with positive integers. Specifically, the first row is filled with numbers from the set $\{1, \ldots, 2023\}$. It turned out that for any two columns the difference of numbers from the first row is divisible by the difference of numbers from the second row, while all numbers in the second row are pairwise different. Is it true for sure that the numbers in the first row are equal? Ivan Kukharchuk

On the table there are $2n$ coins that look the same. It is known that $n$ of them weigh 9 g. each, while the remaining $n$ weigh 10 g. each. It is required to split the coins into $n$ pairs with total weight of each pair 19 g. Prove that this can be done in less than $n$ weighings using a balance without additional weights (the balance shows which pan is heavier or that their weight is equal).

1. Every square of a $8 \times 8$ board is filled with a positive integer, such that the following condition holds: if a chess knight can move from some square to another then the ratio of numbers from these two squares is a prime number. Is it possible that some square is filled with 5 , and another one with 6 ? Egor Bakaev

2. A unit square paper has a triangle-shaped hole (vertices of the hole are not on the border of the paper). Prove that a triangle with area of $1 / 6$ can be cut from the remaining paper. Alexandr Yuran

3. Let us call a bi-squared card $2 \times 1$ regular, if two positive integers are written on it and the number in the upper square is less than the number in the lower square. It is allowed at each move to change both numbers in the following manner: either add the same integer (possibly negative) to both numbers, or multiply each number by the same positive integer, or divide each number by the same positive integer. The card must remain regular after any changes made. What minimal number of moves is sufficient to get any regular card from any other regular card? Alexey Glebov

4. A triangle $A B C$ with angle $A$ equal to $60^{\circ}$ is given. Its incircle is tangent to side $A B$ at point $D$, while its excircle tangent to side $A C$, is tangent to the extension of side $A B$ at point $E$. Prove that the perpendicular to side $A C$, passing through point $D$, meets the incircle again at a point equidistant from points $E$ and $C$. (The excircle is the circle tangent to one side of the triangle and to the extensions of two other sides.) Azamat Mardanov

5. Tom has 13 weight pieces that look equal, however 12 of them weigh the same and the 13th piece is fake and weighs more than the others. He also has two balances: one shows correctly which pan is heavier or that their weights are equal, the other one gives the correct result when the weights on the pans differ, and gives a random result when the weights are equal. (Tom does not know which balance is which). Tom can choose the balance before each weighting. Prove that he can surely determine the fake weight piece in three weighings. Andrey Arzhantsev

6. The baker has baked a rectangular pancake. He then cut it into $n^{2}$ rectangles by making $n-1$ horizontal and $n-1$ vertical cuts. Being rounded to the closest integer, the areas of resulting rectangles equal to all positive integers from 1 to $n^{2}$ in some order. For which maximal $n$ could this happen? (Half-integers are rounded upwards.) Georgy Karavaev

7. There are 100 chess bishops on white squares of a $100 \times 100$ chess board. Some of them are white and some of them are black. They can move in any order and capture the bishops of opposing color. What number of moves is sufficient for sure to retain only one bishop on the chess board?

1. Baron Munchhausen was told that some polynomial $P(x)=a_{n} x^{n}+\ldots+a_{1} x+a_{0}$ is such that $P(x)+P(-x)$ has exactly 45 distinct real roots. Baron doesn't know the value of $n$. Nevertheless he claims that he can determine one of the coefficients $a_{n}, \ldots, a_{1}, a_{0}$ (indicating its position and value). Isn't Baron mistaken? Boris Frenkin

2. There are three hands on a clock. Each of them rotates in a normal direction at some non-zero speed, which can be wrong. In the morning the long and the short hands coincided. Just in three hours after that moment the long and the mid-length hands coincided. After next four hours the short and the mid-length hands coincided. Will it necessarily occur that all three hands will coincide? Alexandr Yuran

3. Consider all 100-digit positive integers such that each decimal digit of these equals $2,3,4,5,6$, or 7 . How many of these integers are divisible by $2^{100}$ ? Pavel Kozhevnikov

4. Given is an acute-angled triangle $A B C, H$ is its orthocenter. Let $P$ be an arbitrary point inside (and not on the sides) of the triangle $A B C$ that belongs to the circumcircle of the triangle $A B H$. Let $A^{\prime}, B^{\prime}$, $C^{\prime}$ be projections of point $P$ to the lines $B C, C A, A B$. Prove that the circumcircle of the triangle $A^{\prime} B^{\prime} C^{\prime}$ passes through the midpoint of segment $C P$. Alexey Zaslavsky

5. Nine farmers have a checkered $9 \times 9$ field. There is a fence along the boundary of the field. The entire field is completely covered with berries (there is a berry in every point of the field, except the points of the fence). The farmers divided the field along the grid lines in 9 plots of equal area (every plot is a polygon), however they did not demarcate their boundaries. Each farmer takes care of berries only inside his own plot (not on its boundaries). A farmer will notice a loss only if at least two berries disappeared inside his plot. There is a crow which knows all of the above, except the location of boundaries of plots. Can the crow carry off 8 berries from the field so that for sure no farmer will notice this? Tatiana Kazitsina

1. A strip for playing "hopscotch" consists of ten squares numbered consecutively $1,2, \ldots, 10$. Clarissa and Marissa start from the center of the first square, jump 9 times to the centers of the other squares so that they visit each square once, and end up at the tenth square. (Jumps forward and backward are allowed.) Each jump of Clarissa was for the same distance as the corresponding jump of Marissa. Does this mean that they both visited the squares in the same order? Alexey Tolpygo

2. The quadrilateral $A B C D$ is convex. Its sides $A B$ and $C D$ are parallel. It is known that the angles $D A C$ and $A B D$ are equal. Furthermore the angles $C A B$ and $D B C$ are equal. Is $A B C D$ necessarily a square? Alexandr Terteryan

3. Eight farmers have a checkered $8 \times 8$ field. There is a fence along the boundary of the field. The entire field is completely covered with berries (there is a berry in every point of the field, except the points of the fence). The farmers divided the field along the grid lines in 8 plots of equal area (every plot is a polygon), however they did not demarcate their boundaries. Each farmer takes care of berries only inside his own plot (not on its boundaries). A farmer will notice a loss only if at least two berries disappeared inside his plot. There is a crow which knows all of the above, except the location of boundaries of plots. Can the crow carry off 9 berries from the field so that for sure no farmer will notice this? Tatiana Kazitsyna

4. There are several (at least two) positive integers written along the circle. For any two neighboring integers one is either twice as big as the other or five times as big as the other. Can the sum of all these integers equal 2023 ? Sergey Dvoryaninov

5. Alice and Bob have found 100 bricks of the same size, 50 white and 50 black. They came up with the following game. A tower will mean one or several bricks standing on top of one another. At the start of the game all bricks lie separately, so there are 100 towers. In a single turn a player must put one of the towers on top of another tower (no flipping towers allowed) so that the resulting tower has no same-colored bricks next to each other. The players make moves in turns, Alice starts first. The one unable to make the next move loses the game. Who can guarantee the win regardless of the opponent's strategy?