//By SiriusRen

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

int n,cpy[],b[],c[],f[],jy,xx,top,k;

int main(){

    scanf("%d",&n);

    for(int i=;i<=n;i++)scanf("%d",&cpy[i]);

    for(int i=;i<=n;i++){

        scanf("%d",&xx),jy=;

        while(xx){

            if(xx>=(<<jy))c[++top]=(<<jy),xx-=(<<jy);

            else c[++top]=xx,xx=;

            b[top]=cpy[i]*c[top],jy++;

        }

    }

    scanf("%d",&k);

    memset(f,0x3f,sizeof(f)),f[]=;

    for(int i=;i<=top;i++)

        for(int j=k;j>=b[i];j--)

            f[j]=min(f[j],f[j-b[i]]+c[i]);

    printf("%d\n",f[k]);

}