Problem

Source: Tournament of Towns, Fall 2002, Junior O Level, P4

Tags: combinatorics proposed, combinatorics



$2002$ cards with numbers $1,2,\ldots ,2002$ written on them are put on a table face up. Two players $A,B$ take turns to pick up a card until all are gone. $A$ goes first. The player who gets the last digit of the sum of his cards larger than his opponent wins. Who has a winning strategy and how should one play to win?