//fast version
#include<cstdio>
#include<algorithm>
using namespace std;
const int N = 100000 + 5, M = 100000 + 5;
typedef long long ll;

int main()
{
	ll ans=0;
	static int n, m, meteorite[N], machine[N];
	scanf("%d%d", &n, &m);
	for(int i=0; i<n; ++i) scanf("%d", &meteorite[i]);
	for(int i=0; i<m; ++i) scanf("%d", &machine[i]);
	sort(meteorite, meteorite+n);
	sort(machine, machine+m);
	for(int i=n-1, j=m-1; i>=0 && j>=0; --i)
	{
		if(meteorite[i]>machine[j]) continue;
		ans += (ll)meteorite[i];
		--j;
	}
	printf("%lld\n", ans);
}