# include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int w[100010],v[100010],stk[4000010],lc[4000010],rc[4000010],sz[4000010],tot=0;
ll len[4000010],sum[4000010],val[4000010],maxn[4000010],addmk[4000010];
bool flag[4000010];
mt19937 rnd(0);
int getid(){return stk[0]?stk[stk[0]--]:++tot;}
int newnode(ll L,ll V)
{
	int cur=getid();
	sz[cur]=1;
	addmk[cur]=lc[cur]=rc[cur]=0;
	sum[cur]=len[cur]=L;
	maxn[cur]=val[cur]=V;
	return cur;
}
int copy(int rt)
{
	int cur=getid();
	tie(lc[cur],rc[cur],sz[cur],len[cur],sum[cur],val[cur],maxn[cur],addmk[cur])=make_tuple(lc[rt],rc[rt],sz[rt],len[rt],sum[rt],val[rt],maxn[rt],addmk[rt]);
	return cur;
}
void pushup(int rt)
{
	sz[rt]=sz[lc[rt]]+sz[rc[rt]]+1;
	sum[rt]=sum[lc[rt]]+sum[rc[rt]]+len[rt];
	maxn[rt]=max(val[rt],max(maxn[lc[rt]],maxn[rc[rt]]));
}
void update(int rt,int x){val[rt]+=x;maxn[rt]+=x;addmk[rt]+=x;}
void pushdown(int rt)
{
	if(addmk[rt])
	{
		if(lc[rt]) update(lc[rt]=copy(lc[rt]),addmk[rt]);
		if(rc[rt]) update(rc[rt]=copy(rc[rt]),addmk[rt]);
		addmk[rt]=0;
	}
}
void split(int rt,ll k,int &x,int &y)
{
	if(!rt) return x=y=0,void();
	pushdown(rt);
	if(k<=sum[lc[rt]]) return y=copy(rt),split(lc[rt],k,x,lc[y]),pushup(y);
	else if(k>=sum[lc[rt]]+len[rt]) return x=copy(rt),split(rc[rt],k-sum[lc[rt]]-len[rt],rc[x],y),pushup(x);
	else
	{
		x=newnode(k-sum[lc[rt]],val[rt]);
		y=newnode(len[rt]-len[x],val[rt]);
		lc[x]=lc[rt];rc[y]=rc[rt];
		pushup(x);pushup(y);
	}
}
int merge(int r1,int r2)
{
	if(!r1 || !r2) return r1+r2;
	pushdown(r1);pushdown(r2);
	int rt;
	if(rnd()%(sz[r1]+sz[r2])<sz[r1]) rt=copy(r1),rc[rt]=merge(rc[r1],r2);
	else rt=copy(r2),lc[rt]=merge(r1,lc[r2]);
	pushup(rt);
	return rt;
}
void dfs(int rt)
{
	if(!rt || flag[rt]) return;
	flag[rt]=1;
	dfs(lc[rt]);dfs(rc[rt]);
}
int main()
{
	int n,rt;
	ll m;
	cin>>n>>m;
	for(int i=1;i<=n;i++) scanf("%d",&w[i]);
	for(int i=1;i<=n;i++) scanf("%d",&v[i]);
	rt=newnode(m+1,0);
	for(int i=n;i;i--)
	{
		int a,b,c,d;
		split(rt,w[i],a,b);
		split(rt,m-w[i]+1,c,d);
		if(c) update(c,v[i]);
		rt=merge(a,c);
		if(i%10000==0)
		{
			dfs(rt);
			stk[0]=0;
			for(int j=1;j<=tot;j++)
				if(flag[j]) flag[j]=0;
				else stk[++stk[0]]=j;
		}
	}
	cout<<maxn[rt]<<endl;
	return 0;
}