#include <bits/stdc++.h>
using namespace std;
const int maxn = 100000 + 5;
int b[maxn];
int g[maxn];
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d", &b[i]);
  for (int i = 1; i <= m; i++) scanf("%d", &g[i]);
  long long sum = 0;
  sort(b + 1, b + n + 1);
  sort(g + 1, g + m + 1);
  if (b[n] > g[1])
    printf("-1\n");
  else {
    int cur = m;
    for (int i = n; i >= 1; i--) {
      sum += (long long)b[i] * m;
      int k = m;
      if (cur == m) {
        while (k > 0 && cur >= 2 && g[cur] > b[i]) {
          k--;
          sum += g[cur] - b[i];
          cur--;
        }
      } else {
        while (k > 0 && cur >= 1 && g[cur] > b[i]) {
          k--;
          sum += g[cur] - b[i];
          cur--;
        }
      }
      while (cur >= 1 && g[cur] == b[i]) cur--;
    }
    if (cur >= 1)
      printf("-1\n");
    else
      printf("%I64d\n", sum);
  }
  return 0;
}
