#include<bits/stdc++.h>
using namespace std;
const int N=2010;
#define int long long
#define pii pair<int,int>
int x[N],p[N],n;vector<int>g[N];vector<pii>bl[N],q;
void dfs(int u){
//	cout<<u<<" frfr "<<endl;
	if(g[u].size()==0){
		if(x[u]>0)bl[u].push_back({0,x[u]});
		return ;
	}
	for(int i:g[u]){
		dfs(i);
		if(bl[i].size())
		for(pii j:bl[i]){
			bl[u].push_back(j);
		}
	}
	if(bl[u].size())
	sort(bl[u].begin(),bl[u].end());
	q.clear();
	if(x[u]>=0){
		if(!bl[u].size())bl[u].push_back({0,0});
		bl[u][0].first-=x[u];
		bl[u][0].first=max(bl[u][0].first,0ll);
		bl[u][0].second+=x[u];
	}else{
		int sig=0,sgg=0;
		int end=0;
		for(int i=0;i<bl[u].size();i++){
			sig+=bl[u][i].first,sgg+=bl[u][i].second;
			if(sgg+x[u]>0){
				end=i+1;q.push_back({sig-x[i],sgg+x[u]});
				break;
			}
		}
		for(int j=end;j<bl[u].size();j++){
			q.push_back(bl[u][j]);
		}
		bl[u]=q;
	}
	sort(bl[u].begin(),bl[u].end());
/*	for(int i=0;i<bl[u].size();i++){
		cout<<u<<" "<<i<<" "<<bl[u][i].first<<" "<<bl[u][i].second<<endl;
	}*/
}
int pres,s;
signed main(){
	cin>>n>>s;pres=s;
	for(int i=1;i<=n;i++){
		scanf("%lld%lld",&x[i],&p[i]);
		g[p[i]].push_back(i);
	}
	dfs(0);
	for(int i=0;i<bl[0].size();i++){
		pii cur=bl[0][i];
		if(cur.first>s)break;
		s+=cur.second;
	}
	cout<<s-pres<<endl;
}