#include <bits/stdc++.h>
using namespace std;
const int N = 1000 * 100 + 10;
vector<int> adj[N];
pair<int, int> p[N];
bool mark[N], mark2[N];
int DFS(int v) {
  mark2[v] = 1;
  for (int u : adj[v]) {
    if (!mark2[u]) return DFS(u);
  }
  return v;
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n, pt = 0, u;
  bool flag = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> u;
    adj[i].push_back(--u);
    mark[u] = 1;
  }
  for (int i = 0; i < n; i++) {
    if (!mark[i]) p[pt++] = make_pair(i, DFS(i));
  }
  for (int i = 0; i < n; i++) {
    if (!mark2[i]) {
      DFS(i);
      flag = 1;
      p[pt++] = make_pair(i, i);
    }
  }
  if (pt == 1 && flag)
    cout << "0\n";
  else {
    cout << pt << endl;
    for (int i = 0; i < pt - 1; i++)
      cout << p[i].second + 1 << " " << p[i + 1].first + 1 << endl;
    cout << p[pt - 1].second + 1 << " " << p[0].first + 1 << endl;
  }
  return 0;
}
