Can anyone help me with this problem;

Let n ≤ 2 be an integer. Given a sequence of n integers a1,

a2,...,an, show that there exist consecutive terms in the sequence whose sum

is divisible by n. That is, show that there are i and j, with 1 ≤i ≤j ≤n,

such that:

sij= ai + ai + 1 + · · · + aj ≡ 0 (mod n)

Thanks