#include<bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include"debug.h"
#else
#define debug(...) void()
#endif
#define all(x) (x).begin(),(x).end()
template<class T>
auto ary(T *a,int l,int r){
	return vector<T>{a+l,a+1+r};
}
using ll=long long;
using ull=unsigned ll;
const int N=3e5+10;
int n,a[N];
ll m;
vector<int>to[N];
struct node{
	ll x,y;
	bool operator < (const node &a)const{
		return -x<-a.x;
	}
	node operator + (const node &a)const{
		if(y>a.x)return {x,y-a.x+a.y};
		else return {x-y+a.x,a.y};
	}
};
priority_queue<node>q[N];
void dfs(int u){
	for(int v:to[u]){
		dfs(v);
		if(q[u].size()<q[v].size())q[u].swap(q[v]);
		for(;!q[v].empty();q[v].pop())q[u].push(q[v].top());
	}
	node t;
	if(a[u]>0)t={0,a[u]};
	else t={-a[u],0};
	for(;!q[u].empty()&&(q[u].top()<t||t.x>=t.y);){
		t=t+q[u].top(),q[u].pop();
	}
	if(t.y>=t.x)q[u].push(t);
}
int main(){
	scanf("%d%lld",&n,&m);
	for(int i=1,x;i<=n;i++){
		scanf("%d%d",&a[i],&x);
		to[x].push_back(i);
	}
	dfs(0);
	ll ans=m;
	for(;!q[0].empty();){
		node t=q[0].top();
		q[0].pop();
		// debug(t.x,t.y);
		if(ans>=t.x)ans+=t.y-t.x;
		else break;
	}
	cout<<ans-m<<endl;
	return 0;
}
#ifdef DEBUG
#include"debug.hpp"
#endif