N = int(input())
P = list(map(int, input().split()))
P = [p - 1 for p in P]

g = [list() for i in range(N)]
called = [False] * N
for i in range(N):
    if P[i] != -1:
        g[i].append(P[i])
        called[P[i]] = True

is_ss = [False] * N
for i in range(N):
    if not called[i] and P[i] != -1 and P[P[i]] != -1:
        v = P[P[i]]
        is_ss[v] = True
ans = sum(is_ss)
print(ans)