#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
vector<int> a,b;
int n,m,x;
long long cost;
int main(){
freopen ("toys.in","r",stdin);

     scanf("%d%d",&n,&m);
for(int i =0; i<n;i++){
    scanf("%d",&x);
    a.push_back(x);
}
sort(a.begin(),a.end());

for(int i = 0; i<m;i++){
    scanf("%d",&x);
    b.push_back(x);
}
sort(b.begin(),b.end());
int count = min(n,m);

for(int i = 0;i<=count;i++){
    cost+=a[n-i]*b[m-i];
}
freopen ("toys.out", "w" , stdout);
cout<<cost<<endl;
return 0;}