n = int(input())
p = list(map(int, input().split()))
for i in range(n):
    p[i] -= 1
d = [0] * n
for i in range(n):
    if p[i] == -1:
        continue
    d[p[i]] += 1
s = [False] * n
for i in range(n):
    if d[i] == 0:
        if p[i] != -1 and p[p[i]] != -1:
            s[p[p[i]]] = True
cnt = 0
for i in range(n):
    if s[i]:
        cnt += 1
print(cnt)