#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;cin>>n;
  vector<int> a(n+1); for(int i=1;i<=n;i++) cin>>a[i];
  int count=0;
  for(int i=1;i<=n;i++){
  	if(i==a[a[i]]) count++;
  }
  cout<<count/2<<endl;
}