#include <stdio.h>
#include <stdlib.h>
#include <algorithm>

using namespace std;

struct greater
{
    template<class T>
    bool operator()(T const &a, T const &b) const { return a > b; }
};

int main()
{
    freopen ("toys.in", "r", stdin);
    freopen ("toys.out", "w" , stdout);

    int N, M, a;
    scanf("%d %d", &N, &M);

    int n[N];
    for(int i=0;i<N;i++){
        scanf("%d", &a);
        n[i]=a;
    }

    int m[M];
    for(int i=0;i<M;i++){
        scanf("%d", &a);
        m[i]=a;
    }

    std::sort(n, n + N, greater());
    std::sort(m, m + M, greater());


    long long ans = 0;
    for(int i=0;i<N;i++){
        ans += (long long) n[i] * m[i];
    }

    printf("%I64d\n", ans);
    return 0;
}