n = int(input())
input_list, tmp_list, check_list = [], [], []

for i in range(n):
    input_list.extend(map(int, (input().split())))

tmp_list.extend(input_list)

powerup_counter = 0
for e in input_list:
    if e in check_list:
        continue
    if input_list.count(e) >= 2:
        powerup_counter += input_list.count(e) // 2
        for i in range(input_list.count(e) // 2 * 2):
            tmp_list.remove(e)
            check_list.append(e)

if len(tmp_list) >= 4:
    powerup_counter += len(tmp_list) // 4

print(powerup_counter)