#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e6 + 5;
inline int read() {
  int bj = 0, hhh = 0;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') bj = 1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    hhh = (hhh << 1) + (hhh << 3) + (ch - '0');
    ch = getchar();
  }
  return bj ? -hhh : hhh;
}
int n, cnt, son[MAX], rd[MAX], vis[MAX];
vector<pair<int, int> > link;
int DFS(int x) {
  vis[x] = 1;
  if (!vis[son[x]])
    return vis[x] = DFS(son[x]);
  else
    return vis[x] = x;
}
int main() {
  n = read();
  for (int i = 1; i <= n; i++) son[i] = read(), rd[son[i]]++;
  for (int i = 1; i <= n; i++)
    if (!rd[i]) cnt++, link.push_back(make_pair(i, DFS(i)));
  for (int i = 1; i <= n; i++)
    if (!vis[i]) link.push_back(make_pair(i, DFS(i)));
  if (link.size() == 1 && !cnt) {
    puts("0");
    return 0;
  }
  printf("%d\n", link.size());
  for (int i = 0, N = link.size(); i < N; i++)
    printf("%d %d\n", link[i].second, link[(i + 1) % N].first);
  return 0;
}
