n = int(input())

ls = [0] * (10 + 1)
for i in range(n):
    for j in map(int, input().split()):
        ls[j] += 1

ct = 0
for i in range(1, 10 + 1):
    ct += ls[i] // 2 + (ls[i] % 2) * 0.25

print(int(ct))