#include <bits/stdc++.h>
using namespace std;
int n,k;
struct Pig{
    int a,p;
}pig[1001];
bool cmp(Pig x,Pig y){
    return x.p>y.p;
}
int f[1001][1001];
int main()
{
    freopen("pig.in","r",stdin);
    freopen("pig.out","w",stdout);
    cin>>n>>k;
    for(int i=1;i<=n;i++){
        cin>>pig[i].a;
    }
    for(int i=1;i<=n;i++){
        cin>>pig[i].p;
    }
    sort(pig+1,pig+1+n,cmp);
    for(int i=1;i<=n;i++){
        for(int j=1;j<=k;j++){
            f[i][j]=max(f[i-1][j],f[i-1][j-1]+max(pig[i].a-pig[i].p*(j-1),0));
            f[i][j]=max(f[i][j],f[i][j-1]);
        }
    }
    cout<<f[n][k]<<endl;
    fclose(stdin);
    fclose(stdout);
}