// Hydro submission #66de78ce73d92a7adbef7e53@1725855950521
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
#define int long long
#define ull unsigned long long
#define SZ(x) ((int)((x).size()))
#define ALL(x) (x).begin(),(x).end()
using namespace std;
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;return x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 300005
#define inf 0x3f3f3f3f3f3f3f3f

// monster hunter order
int n,s,fa[maxn];
pii a[maxn],aa[maxn];

pii operator +(pii a,pii b){
	return mkp(max(a.fi,b.fi-a.se),a.se+b.se);
}
bool cmp(pii a,pii b){
	if((a.fi<a.se+a.fi)!=(b.fi<b.se+b.fi))return a.fi<a.se+a.fi;
	return a.fi<a.se+a.fi?a.fi<b.fi:a.se+a.fi>b.se+b.fi;
}

int ff[maxn];
int getf(int x){
	while(x!=ff[x])x=ff[x]=ff[ff[x]];
	return x;
}

pii tr[maxn<<2];
int id[maxn<<2];
void up(int p){
	if(cmp(tr[p<<1],tr[p<<1|1]))tr[p]=tr[p<<1],id[p]=id[p<<1];
	else tr[p]=tr[p<<1|1],id[p]=id[p<<1|1];
}
void build(int p,int l,int r){
	if(l==r)return tr[p]=a[l],id[p]=l,void();
	int mid=l+r>>1;
	build(p<<1,l,mid),build(p<<1|1,mid+1,r),up(p);
}
void mdf(int p,int l,int r,int x){
	if(l==r)return tr[p]=a[l],void();
	int mid=l+r>>1;
	x<=mid?mdf(p<<1,l,mid,x):mdf(p<<1|1,mid+1,r,x);up(p); 
}

void upd(int u){
	int f=getf(fa[u]);
	//cout<<"u: "<<u<<endl;
	//cout<<"f: "<<f<<"\n";
	assert(getf(u)==u);
	assert(getf(f)==f);
	assert(a[f].se!=-inf);
	a[f]=a[f]+a[u];
	ff[u]=f;
	a[u]=mkp(0,-inf);
//	cout<<"a[f] "<<a[f].fi<<" "<<a[f].se<<"\n";
	if(f!=1) mdf(1,2,n,f);
	mdf(1,2,n,u);
}

signed main()
{
	n=read(),s=read();
	a[1]=mkp(0,0);
	For(i,2,n+1){
		int x=read();
		fa[i]=read()+1;
		if(x>=0) a[i]=mkp(0,x);
		else x=-x,a[i]=mkp(x,-x);
	}
	++n;
	For(i,1,n)ff[i]=i;
	build(1,2,n);
	int res=0;
	For(_,2,n){
		int u=id[1];
		upd(u);
		u=getf(1);
	//	cout<<u<<" "<<a[u].fi<<" "<<a[u].se<<"\n";
		if(a[u].fi<=s) res=max(res,a[u].se);
	}
	cout<<res;
	return 0;
}