#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int cnt = 0;
  for (int i = 0; i < (n); i++) {
    int p;
    cin >> p;
    p--;
    if (p == i) cnt++;
  }
  cout << (cnt + 1) / 2 << endl;
  return 0;
}
