MathDB

4

Part of 2001 India National Olympiad

Problems(1)

Yaphp

Source: INMO 2001 Problem 4

10/10/2005
Show that given any nine integers, we can find four, a,b,c,da, b, c, d such that a+b−c−da + b - c - dis divisible by 2020. Show that this is not always true for eight integers.
modular arithmeticcombinatorics unsolvedcombinatorics