N = int(input())
A = [int(a)-1 for a in input().split()]
S = set()
ex = [False] * N
for a in A :
	if a >= 0 :
		ex[a] = True
for (i, a) in enumerate(A) :
	if not ex[i] and a >= 0:
		b = A[a]
		if b >= 0:
			S.add(b)
print(len(S))