#include<cstdio>

 #include<iostream>

 #include<algorithm>

 #include<cstring>

 #define N 1000005

 #define ll long long

 using namespace std;

 int n,m,tot,w[N],hd[N],ans=;

 ll f[N],g[N],a[N];int mx[N],mn[N];

 struct edge{int v,w,next;}e[N<<];

 char gc(){

     static char s[],*p1,*p2;

     if(p1==p2)p2=(p1=s)+fread(s,,,stdin);

     if(p1==p2)return EOF;

     return *p1++;

 }

 int read(){

     int x=;char ch=gc();

     while(ch>''||ch<'')ch=gc();

     while(ch<=''&&ch>='')x=x*+ch-'',ch=gc();

     return x;

 }

 void adde(int u,int v,int w){

     e[++tot].v=v;

     e[tot].next=hd[u];

     e[tot].w=w;

     hd[u]=tot;

 }

 void dfs1(int u,int fa){

      for(int i=hd[u];i;i=e[i].next){

          int v=e[i].v;

          if(v==fa)continue;

          dfs1(v,u);

          f[u]=max(f[u],f[v]+e[i].w);

      }

 }

 void dfs2(int u,int fa){

     ll mx1=,mx2=;

     for(int i=hd[u];i;i=e[i].next){

         int v=e[i].v;if(v==fa)continue;

         if(f[v]+e[i].w>mx1)mx2=mx1,mx1=f[v]+e[i].w;

         else if(f[v]+e[i].w>mx2)mx2=f[v]+e[i].w;

         g[v]=g[u]+e[i].w;

     }

     for(int i=hd[u];i;i=e[i].next){

         int v=e[i].v;if(v==fa)continue;

         if(f[v]+e[i].w==mx1)g[v]=max(g[v],mx2+e[i].w);

         else if(mx1+e[i].w>g[v])g[v]=mx1+e[i].w;

         dfs2(v,u);

     }

 }

 void solve(){

     for(register int i=;i<=n;i++)a[i]=max(g[i],f[i]);

     int l1=,l2=,r2=,r1=,t=;

     for(register int i=;i<=n;i++){

         while(l1<=r1&&a[i]>=a[mx[r1]])r1--;

         while(l2<=r2&&a[i]<=a[mn[r2]])r2--;

         mx[++r1]=i;mn[++r2]=i;

         while(a[mx[l1]]-a[mn[l2]]>m){

             if(mx[l1]<=mn[l2])t=mx[l1]+,l1++;

             else t=mn[l2]+,l2++;

         }

         ans=max(ans,i-t+);

     }

 }

 int main(){

      n=read();m=read();

      for(register int i=;i<=n;i++){

          int v=read(),w=read();

          adde(i,v,w);adde(v,i,w);

      }dfs1(,);dfs2(,);

      solve();printf("%d",ans);

      return ;

 }