#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#define int long long
#define mkp make_pair
#define fi first
#define se second
using namespace std;
typedef pair<int, int> pii;
const int N = 3e5 + 5;

inline int read(){
	int n=0, f=1; char ch = getchar();
	for(; !isdigit(ch); ch=getchar()) if(ch == '-') f=-1;
	for(; isdigit(ch); ch=getchar()) n=n*10+ch-'0';
	return n*f;
}

struct Edge{
	int nxt, to;
}g[N<<1];

int n, S;
int head[N], ent;
int x[N], fa[N];
int qid[N];
priority_queue<pii, vector<pii>, greater<pii> > q[N];

void add_edge(int u, int v){
	g[++ent].nxt = head[u];
	g[ent].to = v;
	head[u] = ent;
}

int mrg(int u, int v){
	if(q[u].size() > q[v].size()) swap(u, v);
	while(!q[u].empty()) q[v].push(q[u].top()), q[u].pop();
	return v;
}

void add(int u, pii p){
	while(!q[u].empty()){
		pii t = q[u].top();
		if(p.se <= 0){
			q[u].pop();
			p = mkp(max(p.fi, t.fi-p.se), p.se+t.se);
		} else if(p.fi > t.fi){
			q[u].pop();
			p = mkp(p.fi, p.se+t.se);
		} else {
			if(p.se > 0) q[u].push(p);
			break;
		}
	}
	if(q[u].size() == 0 && p.se > 0) q[u].push(p);
}

void dfs(int u){
	if(!~head[u]) qid[u] = u;
	
	for(int i=head[u]; ~i; i=g[i].nxt){
		int v = g[i].to;
		dfs(v);
		if(!qid[u]) qid[u] = qid[v];
		else qid[u] = mrg(qid[u], qid[v]);
	}
//	printf("qid[%lld] = %lld\n", u, qid[u]);
	add(qid[u], mkp(max(0ll, -x[u]), x[u]));
}

signed main(){
	memset(head, -1, sizeof head);
	
	n = read(), S = read();
	for(int i=1; i<=n; i++){
		x[i] = read(), fa[i] = read();
		add_edge(fa[i], i);
	}
	
	dfs(0);
	
	int ans = 0;
	while(!q[qid[0]].empty()){
		int mn = q[qid[0]].top().fi, s = q[qid[0]].top().se; q[qid[0]].pop();
//		printf("mn = %lld, s = %lld\n", mn, s);
		if(S+ans >= mn) ans += s;
	}
	
	printf("%lld\n", ans);
}