# include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ll;
int w[100010],v[100010],rt[2],lc[5000010],rc[5000010],sz[5000010],cnt=0,tot=0;
ll len[5000010],sum[5000010],val[5000010],addmk[5000010];
pair<ll,ll> a[100010];
mt19937 rnd(0);
int newnode(ll L,ll V)
{
	sz[++tot]=1;val[tot]=V;
	addmk[tot]=lc[tot]=rc[tot]=0;
	sum[tot]=len[tot]=L;
	return tot;
}
int copy(int rt)
{
	tot++;
	tie(lc[tot],rc[tot],sz[tot],len[tot],sum[tot],val[tot],addmk[tot])=make_tuple(lc[rt],rc[rt],sz[rt],len[rt],sum[rt],val[rt],addmk[rt]);
	return tot;
}
void pushup(int rt)
{
	sz[rt]=sz[lc[rt]]+sz[rc[rt]]+1;
	sum[rt]=sum[lc[rt]]+sum[rc[rt]]+len[rt];
}
void update(int rt,int x){val[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) return;
	pushdown(rt);
	dfs(lc[rt]);
	a[++cnt]={len[rt],val[rt]};
	dfs(rc[rt]);
}
int build(int l,int r)
{
	if(l>r) return 0;
	int mid=(l+r)/2,rt=newnode(a[mid].first,a[mid].second);
	lc[rt]=build(l,mid-1);
	rc[rt]=build(mid+1,r);
	pushup(rt);
	return rt;
}
int main()
{
	int n;
	ll m,ans=0;
	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[n+1&1]=newnode(m+1,0);
	for(int i=n;i;i--)
	{
		int a,b,c,d;
		split(rt[i+1&1],w[i],a,b);
		split(rt[i+1&1],m-w[i]+1,c,d);
		update(c,v[i]);
		rt[i&1]=merge(a,c);
		if(i%2000==0)
		{
			cnt=tot=0;dfs(rt[i&1]);
			rt[i&1]=build(1,cnt);
		}
	}
	cnt=0;dfs(rt[1]);
	for(int i=1;i<=cnt;i++) ans=max(ans,a[i].second);
	cout<<ans<<endl;
	return 0;
}