/*
ID: espr1t
TASK: 
KEYWORDS: 
*/

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>

using namespace std;
FILE *in; FILE *out;

const int MAX = 5005;

int n, m;
int cnt[MAX], price[MAX];

string toString(long long num) {
    if (num == 0)
        return "0";
    string sign = "";
    if (num < 0)
        sign = "-", num = -num;
    
    string ret;
    while (num)
        ret += (num % 10 + '0'), num /= 10;
    reverse(ret.begin(), ret.end());
    return sign + ret;
}

int main(void) {
	in = stdin; out = stdout;
	in = fopen("toys.in", "rt"); out = fopen("toys.out", "wt");
	
	fscanf(in, "%d %d", &n, &m);
	for (int i = 0; i < n; i++)
	    fscanf(in, "%d", &cnt[i]);
	sort(cnt, cnt + n), reverse(cnt, cnt + n);
	for (int i = 0; i < m; i++)
	    fscanf(in, "%d", &price[i]);
	sort(price, price + m), reverse(price, price + m);
	
	long long ans = 0;
	for (int i = 0; i < n; i++)
	    ans += cnt[i] * price[i];
	
	fprintf(out, "%s\n", toString(ans).c_str());
	
	return 0;
}