#include <bits/stdc++.h>
using namespace std;
void codeRed98() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
}
int main() {
  codeRed98();
  long long int n;
  cin >> n;
  vector<long long int> arr(n);
  vector<bool> w(n, false);
  for (long long int i = 0; i < n; i++) {
    cin >> arr[i];
    arr[i]--;
    w[arr[i]] = true;
  }
  vector<long long int> color(n, 0);
  vector<long long int> c(n);
  long long int a = 0, b = -1;
  vector<pair<long long int, long long int> > comp;
  for (long long int i = 0; i < n; i++)
    if (!w[i]) {
      long long int index = i;
      while (color[index] == 0) {
        color[index] = 2;
        index = arr[index];
      }
      comp.push_back(make_pair(i, index));
    }
  long long int cyc = 0;
  for (long long int i = 0; i < n; i++)
    if (color[i] == 0) {
      long long int index = i;
      while (color[index] == 0) {
        color[index] = 2;
        index = arr[index];
      }
      cyc++;
      comp.push_back(make_pair(i, i));
    }
  if (comp.size() == 1 && cyc == 1) {
    cout << 0;
    return 0;
  }
  cout << comp.size() << endl;
  for (long long int i = 1; i < comp.size(); i++)
    cout << comp[i - 1].second + 1 << " " << comp[i].first + 1 << endl;
  cout << comp[comp.size() - 1].second + 1 << " " << comp[0].first + 1 << endl;
  return 0;
}
