#include<bits/stdc++.h>
using namespace std;
int n;
const int M=1e5+2;
long long a[M],b[M];
long long l,r,c;
int check(long long m){
	long long sum=0;
	for(int i=1;i<=n;i++){
        if(b[i]>m)continue;
        if(b[i]>=l) //普通情况
            sum +=(m-b[i])/a[i]+1;
		else//其他情况
            sum+=((m-b[i])/a[i]-(l-1-b[i])/a[i]);
        if(sum>=c) return 1;
	}
	
	return 0;
}
signed main(){//和int一样
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
//快读，可以不写。
	cin>>n;
	for(int i=1;i<=n;i++) cin>>a[i];
	for(int i=1;i<=n;i++) cin>>b[i];
	cin>>l>>r>>c;
	long long l1=1,r1=r;
	long long ans=-1;
	while(l1<=r1){
		long long mid=(r1+l1)/2;
		if(check(mid)){
			r1=mid-1;
			ans=mid;
		}
		else
			l1=mid+1;
	}
	if(ans==-1) cout<<-1;
    else
        cout<<ans ;
	return 0;
}