n = int(input())
P = list(map(int, input().split()))
A = [0] * n
for p in P:
    if p:
        A[p-1] += 1

B = [0] * n

for i in range(n):
    if not A[i]:
        if P[i]:
            p = P[i]-1
            if P[p]:
                B[P[p]-1] = 1

print(sum(B))