#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long N, M;
  cin >> N >> M;
  vector<long long> v1;
  vector<long long> v2;
  for (long long i = 0; i < N; i++) {
    long long n;
    cin >> n;
    v1.push_back(n);
  }
  for (long long i = 0; i < M; i++) {
    long long n;
    cin >> n;
    v2.push_back(n);
  }
  sort(v1.begin(), v1.end());
  sort(v2.begin(), v2.end());
  if (v1.back() > v2[0]) {
    cout << -1 << '\n';
    return 0;
  }
  long long sum = 0;
  for (long long i = 0; i < N; i++) {
    sum += v1[i] * M;
  }
  if (v1.back() == v2[0]) {
    for (long long i = 0; i < M; i++) {
      sum += v2[i] - v1.back();
    }
    cout << sum << '\n';
  } else {
    reverse(v2.begin(), v2.end());
    for (long long i = 0; i < M - 1; i++) {
      sum += v2[i] - v1.back();
    }
    v1.pop_back();
    sum += v2.back() - v1.back();
    cout << sum << '\n';
  }
  return 0;
}
