#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5;
vector<vector<int>> adj, dadj;
vector<int> ind;
vector<int> pass;
vector<int> curu;
int tmp[100001];
void dfs(int u) {
  if (pass[u]) return;
  pass[u] = 1;
  curu.push_back(u);
  for (auto v : adj[u]) dfs(v);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  dadj = adj = vector<vector<int>>(n + 1);
  pass = ind = vector<int>(n + 1, 0);
  int u;
  for (int i = 1; i <= n; i++) {
    cin >> u;
    dadj[i].push_back(u);
    ind[u] = 1;
    adj[i].push_back(u);
    adj[u].push_back(i);
  }
  vector<pair<int, int>> ans;
  vector<pair<int, int>> comp;
  for (int i = 1; i <= n; i++) {
    if (!pass[i]) {
      dfs(i);
      u = i;
      memset(tmp, 0, sizeof(tmp));
      while (tmp[u] != 1) {
        tmp[u] = 1;
        u = dadj[u][0];
      }
      int isfirst = true;
      for (auto v : curu) {
        if (ind[v] == 0) {
          if (isfirst) {
            isfirst = false;
            comp.emplace_back(u, v);
          } else {
            ans.emplace_back(u, v);
          }
        }
      }
      if (isfirst) comp.emplace_back(u, u);
      curu.clear();
    }
  }
  assert(comp.size() > 0);
  if (comp.size() > 1) {
    for (int i = 0; i < comp.size(); i++)
      ans.emplace_back(comp[i].first, comp[(i + 1) % comp.size()].second);
  } else {
    if (comp[0].first != comp[0].second)
      ans.emplace_back(comp[0].first, comp[0].second);
  }
  cout << ans.size() << endl;
  for (auto x : ans) cout << x.first << " " << x.second << endl;
}
