from collections import defaultdict


N, M = map(int, input().split())
A = list(map(int, input().split()))

r = defaultdict(int)
for i in range(N):
    r[A[i] % M] += 1

ans = 0
for i in range(M // 2 + 1):
    ans += max(r[i], r[M - i])

print(ans)