#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
struct Node {
  int x, fx;
  bool operator<(const Node& ano) const { return fx < ano.x; }
} a[N];
int g[N], h[N];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    a[i].x = i + 1;
    cin >> a[i].fx;
  }
  memset(g, -1, sizeof(g));
  memset(h, -1, sizeof(h));
  int cur = 1;
  for (int it = 0; it < n; it++) {
    if (g[a[it].fx] != -1) {
      if (h[g[a[it].fx]] != a[it].fx) {
        cout << "-1\n";
        return 0;
      }
      g[a[it].x] = g[a[it].fx];
    } else if (g[a[it].x] != -1) {
      if (h[g[a[it].x]] != a[it].fx) {
        cout << "-1\n";
        return 0;
      }
      g[a[it].x] = g[a[it].fx];
    } else {
      g[a[it].x] = cur++;
      h[g[a[it].x]] = a[it].fx;
      g[h[g[a[it].x]]] = g[a[it].x];
    }
  }
  cout << cur - 1 << endl;
  for (int i = 1; i <= n; i++) cout << g[i] << (i == n ? "\n" : " ");
  for (int i = 1; i < cur; i++) {
    cout << h[i] << (i == cur - 1 ? "\n" : " ");
  }
}
