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