n = int(input())
p = [x - 1 for x in map(int, input().split())]
par_cnt = [0] * n
for x in p:
    if x != -1:
        par_cnt[x] += 1
ok = [0] * n
for i in range(n):
    if par_cnt[i] == 0 and p[i] != -1 and p[p[i]] != -1:
        ok[p[p[i]]] = 1
print(sum(ok))