#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]={0};
/*
20 17
76 73 78 69 96 91 53 66 54 82 51 68 91 97 88 57 93 93 98 73 
39 40 23 26 39 33 5 36 31 29 7 26 47 37 26 5 20 23 13 9

377
*/
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;
      return 0;
}