from collections import deque
N = int(input())
P = [int(x) - 1 for x in input().split()]

f = [0] * N
for q in range(N):
    if P[q] == -1:
        continue
    f[P[q]] = 1

st = set()
for q in range(N):
    if f[q] == 1:
        continue
    if P[q] == -1:
        continue

    if P[P[q]] != -1:
        st.add(P[P[q]])

print(len(st))