#include<bits/stdc++.h>

#define ll long long

using namespace std;

const int maxn=;

ll p[maxn],t[maxn],q[maxn],dp[maxn],head,tail,N,Limit;

bool check(ll L)

{

    head=tail=;  q[head]=; dp[]=;

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

        while(tail<head&&i-q[tail]>L) tail++;

        dp[i]=dp[q[tail]]+t[i];

        q[++head]=i;

        while(tail<head&&dp[q[head]]<=dp[q[head-]]) q[head-]=q[head],head--;

    }

    return dp[N]<=Limit;

}

int main()

{

    int i; scanf("%I64d%I64d",&N,&Limit); Limit-=(N-);

    for(i=;i<N;i++) scanf("%d",&p[i]);

    for(i=;i<N;i++) scanf("%d",&t[i]);

    ll L=,R=N-,Mid,Mn=;

    while(L<=R){

        Mid=(L+R)/;

        if(check(Mid)) Mn=Mid,R=Mid-;

        else L=Mid+;

    }

    ll ans=p[Mn];

    for(i=Mn+;i<N;i++) ans=min(p[i],ans);

    printf("%I64d\n",ans);

    return ;

}