import sys

input = sys.stdin.readline


def main():
    N = int(input())
    count = [0]*11
    for i in range(N):
        for v in map(int, input().split()):
            count[v] += 1

    a = 0
    b = 0
    for i in count:
        a += i // 2
        b += i % 2

    print(a + b // 4)


if __name__ == '__main__':
    main()