import sys
input = sys.stdin.readline
N = int(input())
P = list(map(int, input().split()))
R = [[] for _ in range(N)]
for i, p in enumerate(P):
    p-=1
    P[i] = p
    if p==-1:
        continue
    R[p].append(i)
ans = set()
for i in range(N):
    if len(R[i])>0:
        continue
    p = P[i]
    if p==-1:
        continue
    q = P[p]
    if q==-1:
        continue
    ans.add(q)
print(len(ans))