# -*- coding: utf-8 -*- def main(): N = int(input()) history = list() for i in range(N): history.extend(list(map(int, input().split()))) ans = 0 for i in range(1, 11): duplicated = int(history.count(i) / 2) ans = ans + duplicated for n in range(duplicated * 2): history.remove(i) remains = len(history) if remains >= 4: ans = ans + int(remains / 4) print(ans) if __name__ == '__main__': main()