from collections import *

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

for a in A:
    D[a % M] += 1
    D[M - a % M] += 0
    
ans = 0
for k, v in D.items():
    ans += max(D[k], D[M - k])
    
if M % 2 == 0:
    ans -= D[M//2] * 2
    ans += min(1, D[M//2]) * 2
print(ans // 2)