#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
bool reversed(int a,int b){return a > b;}
int main()
{
	freopen ("board.in", "r", stdin);
	freopen ("board.out", "w" , stdout);
	int n, m, answer = 0;
	cin>>n>>m;
	int a[n],b[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, reversed);
	sort(b, b + m, reversed);
	for(int i = 0; i < n; ++i)
	{
		answer += a[i]*b[i];
	}
	cout << answer;

	return 0;
}