#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <ctime>
#include <map>
#include <set>

using namespace std;

int a[5001],b[5001];

int main() {
	freopen("toys.in", "r", stdin);
	freopen("toys.out", "w", stdout);
	int n,m;
	cin >>n>>m;
	for (int i = 0; i < n; ++i) {
		cin>>a[i];
	}
	for (int i = 0; i < m; ++i) {
		cin>>b[i];
	}
	sort(a, a+n);
	sort(b,b+n);
	long long res = 0;
	int j = m-1;
	for (int i = n-1; i >=0; --i) {
		res += a[i]*b[j];
		j--;
	}
	cout << res << endl;
	return 0;
}