11.7

Part of 2000 All-Russian Olympiad Regional Round

Problems(1)

bw numbers 1- N - All-Russian MO 2000 Regional (R4) 11.7

Source:

1, 2, . . .,N

, each of which is colored either black or white. It is allowed to repaint it in the opposite direction color any three numbers, one of which is equal to half the sum of the other two. At which

N

numbers can always be made white?

combinatoricsColoring