#include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <cstring>
#include <climits>
#include <map>
#include <fstream>
#include <stdint.h>
#include <list>
typedef unsigned long long uint64;
typedef long long int64;
using namespace std;
bool visited[1000];

bool odd(int x){
	return x % 2 == 1;
}

bool even(int x){
	return x % 2 == 0;
}

bool BFS(vector<vector<int> >& graph, int dest){
	queue<int> q;
	q.push(1);

	while (!q.empty()){
		int front = q.front();
		visited[front] = true;

		if (front == dest){
			return true;
		}

		q.pop();

		for (int i = 0; i < graph[front].size(); ++i){
			if (!visited[graph[front][i]]){
				q.push(graph[front][i]);
			}
		}
	}
	return false;
}

bool comp(const pair<int, int>& l, const pair<int, int>& r){
	return l.second < r.second;
}

bool gameOver(const vector<vector<int> >& m, int x, int y){

	if (x - 1 >= 0 && y - 1 >= 0){
		//top left
		if (m[x - 1][y] == 1 && m[x][y - 1] == 1 && m[x - 1][y - 1] == 1)
			return true;
	}

	if (x + 1 < m.size() && y - 1 >= 0){
		//top right
		if (m[x][y - 1] == 1 && m[x + 1][y] == 1 && m[x + 1][y - 1] == 1)
		return true;
	}

	if (x - 1 >= 0 && y + 1 < m[0].size()){
		//bottom left
		 if (m[x - 1][y] == 1 && m[x][y + 1] == 1 && m[x - 1][y + 1] == 1)
			return true;
	}

	if (x + 1 < m.size() && y + 1 < m[0].size()){
		//bottom right
		if (m[x + 1][y] == 1 && m[x][y + 1] == 1 && m[x + 1][y + 1] == 1)
			return true;
	}

	return false;
}

int fact(int n){
	if (n == 1)
		return 1;
	else
		return n * fact(n - 1);
}

bool reverseCmp(const int& l, const int& r){
	return l > r;
}

int main(){

	int wantCount, toysCount;
	freopen("toys.in", "r", stdin);
	scanf("%d %d", &wantCount, &toysCount);

	int want[5001] = { 0 };
	int toys[5001] = { 0 };

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

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

	sort(&want[0], &want[wantCount], reverseCmp);
	sort(&toys[0], &toys[toysCount], reverseCmp);

	int count = 0;

	for (int i = 0; i < wantCount; ++i){
		count += (want[i] * toys[i]);
	}

	fclose(stdin);

	freopen("toys.out", "w", stdout);
	printf("%d", count);

	fclose(stdout);


return 0;
}