This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define int long long
struct node{
	int s,e,m;
	pair<long long,int> val;
	long long lazy;
	node *l, *r;
	node(int S, int E){
		s=S; e=E; m=(s+e)/2;
		val={-1e16,s};
		lazy=0;
		if(s!=e){
			l=new node(s,m);
			r=new node(m+1,e);
		}
	}
	void prop(){
		if(s!=e&&lazy){
			l->val.first+=lazy;
			l->lazy+=lazy;
			r->val.first+=lazy;
			r->lazy+=lazy;
			lazy=0;
		}
	}
	void update(int S, int E, long long V){
		if(S<=s&&e<=E){
			val.first+=V;
			lazy+=V;
			return;
		}
		prop();
		if(E<=m) l->update(S,E,V);
		else if(S>m) r->update(S,E,V);
		else l->update(S,m,V),r->update(m+1,E,V);
		val=max(l->val,r->val);
	}
	void pset(int S, long long V){
		if(s==e){
			val.first=V;
			return;
		}
		prop();
		if(S<=m) l->pset(S,V);
		else r->pset(S,V);
		val=max(l->val,r->val);
	}
} *root;
int n;
long long mon;
vector<pair<int,long long> > adj[300005];
int pre[300005],to[300005],pos[300005];
int cur;
void dfs(int x){
	cur++;
	pre[x]=cur;
	to[cur]=x;
	for(auto i:adj[x]) dfs(i.first);
	pos[x]=cur;
}
int done[300005];
pair<int,long long> par[300005];
int32_t main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin >> n >> mon;
	long long org=mon;
	for(int i=1; i<=n; i++){
		long long a,b;
		cin >> a >> b;
		adj[b].push_back({i,a});
		par[i]={b,a};
	}
	dfs(0);
	root=new node(0,n+5);
	root->pset(pre[0],mon);
	while(true){
		pair<long long,int> x=root->val;
		root->pset(x.second,-1e16);
		if(x.first<0) break;
		x.second=to[x.second];
		//cout << x.second << ' ' << x.first << '\n';
		if(x.first>mon){
			root->update(1,cur,x.first-mon);
			mon=x.first;
			int at=x.second;
			while(!done[at]){
				done[at]=1;
				root->update(pre[at],pos[at],-par[at].second);
				at=par[at].first;
			}
			for(auto i:adj[x.second]){
				root->pset(pre[i.first],mon+i.second);
			}
		}
		else{
			for(auto i:adj[x.second]){
				root->pset(pre[i.first],x.first+i.second);
			}
		}
	}
	cout << mon-org;
}
/*6 1
3 0
-3 1
-5 0
2 1
6 3
-4 5*/
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