Submission #993667

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Source Code Expand

#!/usr/bin/env python3
# -*- coding:utf-8 -*-

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals

from collections import Counter
N, M = map(int, input().split())
X = list(map(int, input().split()))
XX = [x % M for x in X]

cc = Counter(X)
c = Counter(XX)

cnt = c[0] // 2
c[0] -= cnt * 2
if M % 2 == 1:
    to = M // 2 + 1
else:
    to = M // 2
    tmp = c[M//2] // 2
    c[M//2] -= tmp * 2
    cnt += tmp

for i in range(1, to):
    # print(i, M-i, c [i], c[M-i])
    tmp = min(c[i], c[M-i])
    cnt += tmp
    c[i] -= tmp
    c[M-i] -= tmp

# print(c)
# print(cc)
for i in cc:
    # print("i = {}, cc[i] = {}".format(i, cc[i]))
    if cc[i] >= 2:
        if c[i % M] >= 2:
            tmp =  c[i % M] // 2
            cnt += tmp
            c[i % M] -= tmp * 2
            # print(cc[i])
            # print(c[i % M],  i, cc[i])
# print(c)
# for i in c:
#     print(i, c[i])

print(cnt)

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