from collections import defaultdict

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

ps = [0] + P
freq = defaultdict(int)
for i in range(1, N+1):
    if ps[i] == 0: continue
    freq[ps[i]] += 1

ans = 0
for i in range(1, N+1):
    if freq[i] > 0: continue
    x = ps[i]
    if x != 0:
        y = ps[x]
        if y != 0 and y != i:
            ans += 1

print(ans)