#include<bits/stdc++.h>
using namespace std;
#define ll long long
char buf[1<<21],*p1=buf,*p2=buf,obuf[1<<21],*o=obuf;
#define g()(p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
inline ll read(){
    ll s=0; int f=1;char c=g();
    for(;c<'0'||c>'9';c=g())
        if(c=='-')f=-1;
    for(;c>='0'&&c<='9';c=g())
        s=s*10+c-'0';
    return s*f;
}
inline void write(ll x,char c){
    static char buf[16];
    static int len=-1;
    if(x<0)putchar('-'),x=-x;
    do buf[++len]=x%10,x/=10;while(x);
    while(len>=0)putchar(buf[len--]+'0');
    putchar(c);
}
pair<int,int> t[500010];
ll hs[500010],th[500010];
map<int,ll> dp[500010];
int n;
ll solve(int id,ll l){
    if(id==n+1) return 0;
    if(l>=hs[id]) return th[id];
    //cout<<id<<" "<<l<<endl;
    if(l<0) return -hs[1];
    if(l==0) return 0;
    if(dp[id][l]) return dp[id][l];
    ll t1=min(l,(ll)t[id].first-1),t2=l-t[id].first;
    //cout<<id<<" "<<l<<" "<<t1<<" "<<t2<<endl;
    if(t2<0) return dp[id][l]=solve(id+1,t1);
    if(t2>=t1) return dp[id][l]=solve(id+1,t2)+t[id].second;
    return dp[id][l]=max(solve(id+1,t2)+t[id].second,solve(id+1,t1));
}
int main(){
    ll l;
    n=read(); l=read();
    for(int i=1;i<=n;++i) t[i].first=read();
    for(int i=1;i<=n;++i) t[i].second=read();
    for(int i=n;i>=1;--i) hs[i]=hs[i+1]+t[i].first,th[i]=th[i+1]+t[i].second;
    write(solve(1,l),'\n');
    return 0;
}