#include <bits/stdc++.h>
using namespace std;
const long long N = 1e5 + 5;
long long indegree[N], node;
bool vis[N];
vector<pair<long long, long long>> v;
vector<long long> G[N];
void dfs(long long u) {
  vis[u] = 1;
  node = u;
  for (long long v : G[u]) {
    if (!vis[v]) {
      dfs(v);
    }
  }
}
int main() {
  long long n, i, j, u, k;
  scanf("%lld", &n);
  for (i = 1; i <= n; i++) {
    scanf("%lld", &u);
    G[i].push_back(u);
    indegree[u]++;
  }
  bool flag = false;
  for (i = 1; i <= n; i++) {
    if (indegree[i] == 0 && !vis[i]) {
      dfs(i);
      v.push_back(make_pair(i, node));
    }
    if (indegree[i] == 0) {
      flag = true;
    }
  }
  for (i = 1; i <= n; i++) {
    if (!vis[i]) {
      dfs(i);
      v.push_back(make_pair(i, node));
    }
  }
  if (!flag && v.size() == 1) {
    printf("0\n");
    return 0;
  }
  cout << v.size() << endl;
  k = v.size();
  for (i = 0; i < k - 1; i++) {
    cout << v[i].second << " " << v[i + 1].first << endl;
  }
  cout << v[k - 1].second << " " << v[0].first << endl;
}
