#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  long long n, m;
  cin >> n >> m;
  vector<long long> v(n);
  vector<long long> v2(m);
  for (long long i = 0; i < n; i++) {
    cin >> v[i];
  }
  for (long long i = 0; i < m; i++) {
    cin >> v2[i];
  }
  sort(v.begin(), v.end());
  sort(v2.begin(), v2.end());
  long long ans = 0;
  for (long long i = 0; i < n; i++) {
    ans += v[i] * m;
  }
  long long j = n - 1;
  long long k = 0;
  for (long long i = 0; i < m; i++) {
    if (j < 0 || v2[i] < v[j]) {
      cout << -1;
      return 0;
    } else if (v2[i] > v[j]) {
      ans = ans - v[j] + v2[i];
      k++;
      if (k == m - 1) {
        j--;
      }
    }
  }
  cout << ans;
}
