#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  cin >> n >> m;
  vector<int> b(n), g(m);
  int cur_max = 0;
  for (int i = 0; i < n; i++) {
    cin >> b[i];
    if (cur_max < b[i]) {
      cur_max = b[i];
    }
  }
  sort(b.begin(), b.end());
  int cur_min = 1000 * 1000 * 1000;
  for (int i = 0; i < m; i++) {
    cin >> g[i];
    if (cur_min > g[i]) {
      cur_min = g[i];
    }
  }
  if (cur_min < cur_max) {
    cout << -1 << endl;
    return 0;
  }
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    ans += (long long)m * b[i];
  }
  int it = n - 1;
  int cnt = 0;
  for (int i = 0; i < m; i++) {
    if (g[i] == cur_max) {
      continue;
    }
    ans += (long long)g[i];
    if (cnt >= m - 1) {
      it--;
      cnt = 0;
    }
    if (it < 0) {
      cout << -1 << endl;
      return 0;
    }
    cnt++;
    ans -= b[it];
  }
  cout << ans << endl;
}
