#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 17;
int n, m, par[maxn], f[maxn], cen[maxn], d[maxn], ptr;
bool mark[maxn], done[maxn];
vector<int> vec, one[maxn];
pair<int, int> edge[maxn];
int r(int v) { return par[v] < 0 ? v : par[v] = r(par[v]); }
void merge(int v, int u) {
  v = r(v), u = r(u);
  if (v == u) return;
  par[u] = v;
}
int get(int v) {
  if (mark[f[v]]) return f[v];
  mark[f[v]] = 1;
  return get(f[v]);
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0);
  memset(par, -1, sizeof par);
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> f[i], f[i]--;
    d[f[i]]++;
    merge(i, f[i]);
  }
  for (int i = 0; i < n; i++) {
    if (!mark[r(i)]) {
      mark[r(i)] = 1;
      cen[r(i)] = get(r(i));
      vec.push_back(cen[r(i)]);
    }
    if (d[i] == 0) one[r(i)].push_back(i);
  }
  for (int i = 0; i < vec.size(); i++) {
    int v = vec[i];
    for (int i = 0; i < (int)one[r(v)].size() - (vec.size() > 1); i++)
      edge[m++] = {v, one[r(v)][i]};
    if (vec.size() > 1)
      edge[m++] = {v, one[r(vec[(i + 1) % vec.size()])].size()
                          ? one[r(vec[(i + 1) % vec.size()])].back()
                          : vec[(i + 1) % vec.size()]};
  }
  cout << m << '\n';
  for (int i = 0; i < m; i++)
    cout << edge[i].first + 1 << ' ' << edge[i].second + 1 << '\n';
  return 0;
}
