import sys;input=sys.stdin.readline
def MI():return map(int,input().split())
def PRINT(ans):
    from collections.abc import Sequence
    if isinstance(ans,bool):
        s='Yes' if ans else 'No'
    elif isinstance(ans,Sequence) and not isinstance(ans,str):
        s='\n'.join(map(str,ans))
    else:
        s=str(ans)
    sys.stdout.write(s+'\n')
INF=10**18
mod=998244353
D4=[(1,0),(-1,0),(0,1),(0,-1)]
D8=D4+[(1,1),(-1,1),(1,-1),(-1,-1)]
#from math import gcd,lcm,log2,sqrt,isqrt
#from collections import deque,defaultdict
#from heapq import heappop,heappush,heapify
#from bisect import bisect_left,bisect_right
#from itertools import permutations,combinations,combinations_with_replacement,product
#from functools import lru_cache
#from atcoder.dsu import DSU
#from atcoder.math import inv_mod
#from atcoder.segtree import Segtree
#from atcoder.fenwicktree import FenwickTree

## main
N=int(input())
A=list(MI())
into=[0]*(N+1)
for x in A:
    if x!=0:
        into[x]+=1
ans=set()
for i in range(1,N+1):
    if into[i]!=0:
        continue
    j=A[i-1]
    if j==0:
        continue
    idx=A[j-1]
    if idx==0:
        continue
    ans.add(idx)
print(len(ans))