Let $n$ be a positive integer. A grid of dimensions $n \times n$ is divided in $n^2$ $1 \times 1$ squares. Every segment of length $1$ (side of a square) from this grid is coloured in blue or red. The number of red segments is not greater than $n^2$. Find all positive integers $n$, for which the grid always will cointain at least one $1 \times 1$ square which has at least three blue sides.