sock-merchant.py

from collections import Counter


def sockMerchant(n, ar):
    return sum(x // 2 for x in Counter(ar).values())


def test_sockMerchant_1():
    ar = [1, 2, 1, 2, 1, 3, 2]
    assert sockMerchant(7, ar) == 2


def test_sockMerchant_2():
    ar = [10, 20, 20, 10, 10, 30, 50, 10, 20]
    assert sockMerchant(9, ar) == 3

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    n = int(input())

    ar = list(map(int, input().rstrip().split()))

    result = sockMerchant(n, ar)

    fptr.write(str(result) + '\n')

    fptr.close()