import collections
N,M = map(int, input().split())
A = list(map(int, input().split()))
CA = collections.Counter()
for a in A:
    CA[a%M]+=1
    CA[M-a%M]+=0
ans = 0
for k,v in CA.items():
    if k*2==M:
        ans+=2
    else:
        ans+=max(CA[k%M],CA[M-k%M])
print(ans//2)