Submission #7927561

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Source Code Expand

N,M=map(int,input().split())
X=list(map(int,input().split()))
from collections import defaultdict
r=[defaultdict(int) for i in range(M)]
for x in X:
    r[x%M][x]+=1
a=sum(r[0].values())//2
for m in range(1,-(-M//2)):
    v1,v2=sum(r[m].values()),sum(r[M-m].values())
    if v1>v2:
        p=sum([e//2 for e in r[m].values()])
        a+=v2+min(p,(v1-v2)//2)
    else:
        p=sum([e//2 for e in r[M-m].values()])
        a+=v1+min(p,(v2-v1)//2)
if M%2==0:
    a+=sum(r[M//2].values())//2
print(a)

Submission Info

Judge Result