N = int(input())
P = list(map(lambda x: int(x)-1, input().split()))

indegs = [0] * N
for i in range(N):
    if P[i] != -1:
        indegs[P[i]] += 1

ans = set()
for i in range(N):
    if indegs[i] > 0: continue
    if P[i] != -1 and P[P[i]] != -1:
        ans.add(P[P[i]])

print(len(ans))