#include <stdio.h>
#include <stdlib.h>
#define M 100001
typedef struct _lnod {int nn; struct _lnod *urm;} lnod;
typedef struct _nod {int v; int t; int V; int niv; lnod *f;} nod;

int q[M],sz=sizeof(lnod),nrdiv,dim;
nod a[M];

int fc(const void *x,const void *y)
{
    return a[*(int *)y].V-a[*(int *)x].V;
}
void proces(int r)
{
    int i=0,v[M]; 
    lnod *p; 
    if(a[r].V>dim) 
    { 
	p=a[r].f; while(p) {v[i++]=p->nn; p=p->urm;} 
	qsort(v,i,sizeof(int),fc); 
	for(i=0;a[r].V>dim;i++) 
	{
	    a[r].V-=a[v[i]].V; 
	    nrdiv++;
	}
    } 
    a[a[r].t].V+=a[r].V;
}
int main()
{
    FILE *fi,*fo;
 
    int i,k,n,rad=0,iq,sq; lnod *p;

    fi=fopen("mese.in","rt");

    fscanf(fi,"%d %d",&n,&dim);

    for(i=1;i<=n;i++) 
    {
	fscanf(fi,"%d %d",&k, &a[i].v); 
	a[i].t=k; 
	a[i].V=a[i].v;
		   
	if(!k) rad=i; 
	else 
	{
	    p=(lnod *)malloc(sz); 
	    p->nn=i; 
	    p->urm=a[k].f; 
	    a[k].f=p;
	} 
    }

    fclose(fi);

    q[1]=rad; 
    iq=sq=1;

    while(iq<=sq) 
    {
	k=q[iq]; 
	a[k].niv=a[a[k].t].niv+1; 
	p=a[k].f;
               
	while(p) 
	{
	    q[++sq]=p->nn; 
	    p=p->urm;
	} 
	    
	iq++;
    }

    for(i=n;i>0;i--) proces(q[i]);

    fo=fopen("mese.out","wt");

    fprintf(fo,"%d\n",nrdiv+1);

    fclose(fo); 
    return 0;
}