#include <bits/stdc++.h>
int f[100005];
int g[100005];
int h[1000005];
int v[100005];
int main() {
  int n, m = 0;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &f[i]);
  }
  for (int i = 1; i <= n; i++) {
    if (v[i] == 0) {
      if (f[i] == i) {
        m++;
        h[m] = i;
        v[i] = m;
        g[i] = m;
      } else {
        if (v[f[i]] == 0) {
          if (f[f[i]] == f[i]) {
            m++;
            h[m] = f[i];
            v[f[i]] = m;
            g[f[i]] = m;
            g[i] = m;
          } else {
            puts("-1");
            return 0;
          }
        } else {
          g[i] = v[f[i]];
        }
      }
    }
  }
  printf("%d\n", m);
  for (int i = 1; i <= n; i++) {
    printf("%d ", g[i]);
  }
  puts("");
  for (int i = 1; i <= m; i++) {
    printf("%d ", h[i]);
  }
  return 0;
}
