N = int(input())

L = [0] * 11
for _ in range(N):
    for i in map(int, input().split()):
        L[i] += 1

C = 0
L2 = [0] * 11
for i in range(11):
    if L[i] >= 2:
        C += L[i] // 2
        L2[i] = L[i] - (L[i]//2 * 2)
    else:
        L2[i] = L[i]

C += L2.count(1) // 4

print(C)