#include <bits/stdc++.h>
using namespace std;

#define int long long

const int N=3e5+5;

int p[N], a[N];
vector <int> g[N];
set <pair<int,int> > s[N];

void dfs(int x)
{
	for(auto to:g[x])
	{
		dfs(to);
		if(s[x].size()<s[to].size())
			swap(s[x],s[to]);

		for(auto p:s[to])
			s[x].insert(p);

		s[to].clear();
	}

	if(a[x]>=0)
		s[x].insert(make_pair(0,a[x]));
	else
	{
		int now=-a[x], sum=a[x];
		while(sum<0 && s[x].size())
		{
			now = max(s[x].begin()->first-sum,now);
			sum += s[x].begin()->second;
			s[x].erase(s[x].begin());
		}

		if(sum<0)
			return;

		auto ed=s[x].end();
		for(auto it=s[x].begin();it!=s[x].end();it++)
			if(it->first>now)
			{
				ed=it;
				break;
			}
			else
				sum += it->second;

		s[x].erase(s[x].begin(),ed);

		if(s[x].size() && s[x].begin()->first<=now)
			assert(0);
		s[x].insert(make_pair(now,sum));
	}
}

signed main()
{
	int n,start;
	cin >> n >> start;
	for(int i=1;i<=n;i++)
	{
		scanf("%lld %lld",&a[i+1],&p[i+1]);
		p[i+1]++;
	}
	n++;

	for(int i=2;i<=n;i++)
		g[p[i]].push_back(i);

	dfs(1);

	int ans=0;
	for(auto x:s[1])
		if(start>=x.first)
			start += x.second, ans += x.second;
	printf("%lld\n",ans);
	return 0;
}