#!/usr/bin/env python
# -*- coding: utf-8 -*-
def main():
    n = int(input())
    
    items = {}
    for i in range(n):
        for j in input().split():
            if j in items:
                items[j] += 1
            else:
                items[j] = 1
    pairs = 0
    rest = 0
    for i in items.values():
        pairs += i // 2
        rest += i % 2

    result = pairs + (rest // 4)
    print(result)

if __name__ == '__main__':
    main()