#include <iostream>
#include <fstream>
#include <algorithm>
#define N 1005
using namespace std;
ifstream fin("arme.in");
ofstream fout("arme.out");

int n,m,a[N], b[N];
void Citire()
{
    fin>>n>>m;
    for(int i=1;i<=n;i++)fin>>a[i];
    for(int i=1;i<=m;i++)fin>>b[i];
}
void Greedy()
{
    int s=0, i;
    sort(a+1,a+n+1);///cresc dupa a
    sort(b+1,b+m+1, greater<int>());///desc dupa b
    i=1;
    while(a[i]<b[i] && i<=n && i<=m)
        a[i]=b[i],i++;
    s=0;
    for(i=1;i<=n;i++)s+=a[i];
    fout<<s;
}
int main()
{
  Citire();
  Greedy();
  return 0;
}