Submission #6365387

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Source Code Expand

N,M = map(int,input().split())
*X, = map(int,input().split())

cnt = [0]*(10**5+10)
cntMod = [0]*M
cntPairsMod = [0]*M
for x in X:
    cnt[x] +=1
    cntMod[x%M] +=1
for i,c in enumerate(cnt):
    cntPairsMod[i%M] += (c//2)*2

ans = cntMod[0]//2
if M%2==0:ans += cntMod[M//2]//2
for i in range(1,M//2 +M%2):
    j = M-i
    pairs = min(cntMod[i],cntMod[j])
    ans += pairs
    cntMod[i] -= pairs
    cntMod[j] -= pairs
    ans += min(cntMod[i],cntPairsMod[i])//2
    ans += min(cntMod[j],cntPairsMod[j])//2
print(ans)

Submission Info

Judge Result