#include <bits/stdc++.h>
using namespace std;
const long long inf = 1e18;
const long long mod = 1e9 + 7;
const long long maxn = 1e5 + 10, maxval = 1e9 + 10, mlg = (1 << 18) + 10;
long long mark[maxn], mark_sync[maxn];
vector<long long> nei[maxn][2], source[maxn], sync[maxn];
vector<pair<long long, long long> > ans;
long long n, cnt;
void dfs(long long u) {
  mark[u] = 1;
  if (nei[u][0].empty()) {
    source[cnt].push_back(u);
  }
  for (auto v : nei[u][1]) {
    if (!mark[v]) {
      dfs(v);
    }
  }
  for (auto v : nei[u][0]) {
    if (!mark[v]) {
      dfs(v);
    }
  }
}
void dfs_sync(long long u) {
  mark_sync[u] = 1;
  for (auto v : nei[u][1]) {
    if (!mark_sync[v]) {
      dfs_sync(v);
    } else {
      sync[cnt].push_back(v);
      return;
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  cin >> n;
  for (int i = 0; i < n; i++) {
    long long x;
    cin >> x;
    nei[i + 1][1].push_back(x);
    nei[x][0].push_back(i + 1);
  }
  for (int i = 1; i <= n; i++) {
    if (!mark[i]) {
      dfs(i);
      if (source[cnt].empty()) {
        source[cnt].push_back(i);
        sync[cnt].push_back(i);
      }
      dfs_sync(i);
      cnt++;
    }
  }
  for (int i = 0; i < cnt; i++) {
    for (auto v : source[(i + 1) % cnt]) {
      ans.push_back({sync[i][0], v});
    }
  }
  if (cnt == 1) {
    bool can = true;
    for (int i = 1; i <= n; i++) {
      if (nei[i][0].empty()) {
        can = false;
        break;
      }
    }
    if (can) {
      cout << 0 << endl;
      return 0;
    }
  }
  cout << ans.size() << endl;
  for (auto tmp : ans) {
    cout << tmp.first << ' ' << tmp.second << endl;
  }
}
