#include <bits/stdc++.h>
using namespace std;
int g[200009];
int visited[200009];
int indeg[200009];
int dfs(int u) {
  visited[u] = 1;
  if (!visited[g[u]]) {
    return dfs(g[u]);
  } else {
    return u;
  }
}
int main() {
  int n;
  cin >> n;
  int k = 0;
  vector<int> start;
  vector<int> end;
  for (int i = 1; i <= n; ++i) {
    cin >> g[i];
    indeg[g[i]]++;
  }
  for (int i = 1; i <= n; ++i) {
    if (indeg[i] == 0) {
      k++;
      start.push_back(dfs(i));
      end.push_back(i);
    }
  }
  int p = k;
  for (int i = 1; i <= n; ++i) {
    if (!visited[i]) {
      ++k;
      start.push_back(dfs(i));
      end.push_back(i);
    }
  }
  if (k == 1 && p == 0) {
    cout << 0 << endl;
  } else {
    cout << k << endl;
    for (int i = 0; i < k; ++i) {
      cout << start[i] << ' ' << end[(i + 1) % k] << endl;
    }
  }
}
