#include <bits/stdc++.h>   using namespace std;   int root, n, m, tot, ans, a[2000010], zy[2000010];   bool b[2000010], v[2000010];   void dfs(int k) {     if (b[a[k]]) {       b[a[k]] = v[a[k]] = false;       dfs(a[k]);       v[a[k]] = true;     } else {       if (!v[a[k]]) {         tot++;         if (root == 0) {           root = k;           zy[k] = k;         } else           zy[k] = root;       }     }   }   int work(int k) {     if (v[a[k]]) {       v[a[k]] = false;       return (work(a[k]));     } else       return k;   }   int main(int argc, const char* argv[]) {     memset(b, true, sizeof(b));     int i, j, k;     tot = 0;     cin >> n;     root = 0;     for (i = 1; i <= n; ++i) {       scanf( %d , &a[i]);       if (a[i] == i) root = i;       zy[i] = a[i];     }     if (root != 0) tot = -1;     for (i = 1; i <= n; ++i)       if (b[i]) {         b[i] = v[i] = false;         dfs(i);         v[i] = true;       }     cout << tot << endl;     for (i = 1; i <= n; ++i) cout << zy[i] <<    ;     return 0;   }   