N = int(input())
P = list(map(int, input().split()))

F = [False]*N
for p in P:
    if 1 <= p:
        F[p-1] = True

ans = [False]*N
for i in range(N):
    if P[i] == 0:
        continue
    if F[i]:
        continue
    a = P[i]-1
    if P[a] == 0:
        continue
    ans[P[a]-1] = True

print(sum(ans))