#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  vector<long long> f(n + 1);
  for (long long i = 0; i < n; i++) cin >> f[i + 1];
  vector<long long> g(n + 1, -1);
  vector<long long> h;
  long long counter = 1;
  vector<long long> done(n + 1, -1);
  for (long long i = 1; i <= n; i++) {
    if (done[f[i]] != -1) {
      g[i] = done[f[i]];
      continue;
    }
    if (f[f[i]] != f[i]) {
      cout << -1 << endl;
      return 0;
    }
    g[i] = counter;
    done[f[i]] = counter;
    h.push_back(f[i]);
    counter++;
  }
  cout << h.size() << endl;
  for (long long i = 1; i <= n; i++) cout << g[i] << ' ';
  cout << endl;
  for (long long i = 0; i < h.size(); i++) cout << h[i] << ' ';
  cout << endl;
  return 0;
}
