#include <bits/stdc++.h>
using namespace std;
struct comp {
  vector<int> roots;
  int center;
};
int n;
vector<int> g, indeg, vis;
vector<comp> comps;
void dfs(int u) {
  int v = g[u];
  if (vis[v] == -2) {
    comps.push_back(comp{vector<int>(), v});
    vis[u] = comps.size() - 1;
  } else {
    vis[u] = -2;
    if (vis[v] == -1) {
      dfs(v);
    }
    vis[u] = vis[v];
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n;
  g.assign(n, 0);
  indeg.assign(n, 0);
  for (int &x : g) {
    cin >> x, --x;
    ++indeg[x];
  }
  vis.assign(n, -1);
  for (int i = 0; i < n; ++i) {
    if (vis[i] == -1) {
      dfs(i);
    }
    if (indeg[i] == 0) {
      comps[vis[i]].roots.push_back(i);
    }
  }
  for (comp &it : comps) {
    if (it.roots.size() == 0) {
      it.roots.push_back(it.center);
    }
  }
  vector<pair<int, int> > ans;
  for (int i = 0; i < comps.size(); ++i) {
    for (int v : comps[(i + 1) % comps.size()].roots) {
      if (comps[i].center != v) {
        ans.push_back({comps[i].center, v});
      }
    }
  }
  cout << ans.size() << "\n";
  for (auto &x : ans) {
    cout << x.first + 1 << " " << x.second + 1 << "\n";
  }
}
