# include <bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr double alp=0.2;
int w[100010],v[100010],stk[5000010],lc[5000010],rc[5000010],tot=0,cnt=0;
ll sz[5000010],len[5000010],val[5000010],addmk[5000010];
bool flag[5000010];
int newnode(ll s=0,ll l=0,ll v=0)
{
	int cur=(stk[0]?stk[stk[0]--]:++tot);cnt++;
	assert(cur<=5000000);
	addmk[cur]=lc[cur]=rc[cur]=0;
	sz[cur]=s;
	len[cur]=l;val[cur]=v;
	return cur;
}
int copy(int rt)
{
	int cur=(stk[0]?stk[stk[0]--]:++tot);cnt++;
	assert(cur<=5000000);
	tie(lc[cur],rc[cur],sz[cur],len[cur],val[cur],addmk[cur])=make_tuple(lc[rt],rc[rt],sz[rt],len[rt],val[rt],addmk[rt]);
	return cur;
}
void pushup(int rt)
{
	if(!lc[rt]) return;
	sz[rt]=sz[lc[rt]]+sz[rc[rt]];
	len[rt]=len[lc[rt]]+len[rc[rt]];
	val[rt]=max(val[lc[rt]],val[rc[rt]]);
}
void update(int rt,ll 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;
	}
}
int join(int x,int y)
{
	int rt=newnode();
	lc[rt]=x;rc[rt]=y;
	pushup(rt);
	return rt;
}
int merge(int x,int y)
{
	if(!x || !y) return x+y;
	pushdown(x);pushdown(y);
	if(min(sz[x],sz[y])>=alp*(sz[x]+sz[y])) return join(x,y);
	if(sz[x]>=sz[y])
		if(sz[lc[x]]>=alp*(sz[x]+sz[y])) return merge(lc[x],merge(rc[x],y));
		else return pushdown(rc[x]),merge(merge(lc[x],lc[rc[x]]),merge(rc[rc[x]],y));
	else
		if(sz[rc[y]]>=alp*(sz[x]+sz[y])) return merge(merge(x,lc[y]),rc[y]);
		else return pushdown(lc[y]),merge(merge(x,lc[lc[y]]),merge(rc[lc[y]],rc[y]));
}
void split(int rt,ll k,int &x,int &y)
{
	if(!rt) return x=y=0,void();
	if(sz[rt]==1)
		if(!k) return x=0,y=rt,void();
		else if(k==len[rt]) return x=rt,y=0,void();
		else return x=newnode(1,k,val[rt]),y=newnode(1,len[rt]-k,val[rt]),void();
	pushdown(rt);
	if(k<=len[lc[rt]]) split(lc[rt],k,x,y),y=merge(y,rc[rt]);
	else split(rc[rt],k-len[lc[rt]],x,y),x=merge(lc[rt],x);
}
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(1,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(cnt>4999000)
		{
			cnt=stk[0]=0;dfs(rt);
			for(int i=1;i<=tot;i++)
				if(flag[i]) flag[i]=0,cnt++;
				else stk[++stk[0]]=i;
		}
	}
	cout<<val[rt]<<endl;
	return 0;
}