#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstdio>
using namespace std;
long long n, m, a[5010], b[5010], ans;
int main()
{
    freopen ("toys.in", "r", stdin);
    freopen ("toys.out", "w" , stdout);
    scanf("%lld%lld", &n, &m);
    for (long long i=1; i<=n; i++)
        scanf("%d",&a[i]);
    sort(a+1,a+n+1);
    for (long long i=1; i<=m; i++)
        scanf("%d",&b[i]);
    sort(b+1, b+m+1);
    for (long long i=m, j=n; j>=1; i--, j--)
    {
        ans+=a[j]*b[i];
    }
    printf("%lld\n",ans);
    return 0;
}