//#include "festival.h"
#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("avx2")
#define ll long long
#define ld long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define plx pair<ll,int>
#define f first
#define s second
#define pb push_back
#define all(x) x.begin(),x.end()
#define vi vector<int>
#define vvi vector<vi>
#define ub(x,i) upper_bound(all(x),i)-x.begin()
#define lb(x,i) lower_bound(all(x),i)-x.begin()
#define sz(x) (ll)x.size()
#define cd complex<double>
#define t3 tuple<ll,ll,ll>
using namespace std;
const int mxn=3e5+5;
vector<int>g[mxn];
ll x[mxn]{0},p[mxn];
multiset<pll>ms[mxn];
void dfs(int u,int p){
    for(auto v:g[u]){
        if(v==p)continue;
        dfs(v,u);
        if(ms[v].size()>ms[u].size())swap(ms[u],ms[v]);
        for(auto it : ms[v])ms[u].insert(it);
    }ll st=max((ll)0,-x[u]);
    ll cst=x[u];
    while(cst<0&&!ms[u].empty()){
        auto it = ms[u].begin();
        cst+=it->s;
        st=max(st,it->f-cst);ms[u].erase(it);
    }
    while(!ms[u].empty()&&ms[u].begin()->f<=st){
        cst+=ms[u].begin()->s;
        ms[u].erase(ms[u].begin());
    }
    if(cst<0)return;
    ms[u].insert({st,cst});
}
int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int n;ll s;cin>>n>>s;
    for(int i=1;i<=n;i++){
        cin>>x[i]>>p[i];g[p[i]].pb(i);g[i].pb(p[i]);
    }dfs(0,0);ll rs=s;
    while(!ms[0].empty()&&rs>=ms[0].begin()->f){
        rs+=ms[0].begin()->s;ms[0].erase(ms[0].begin());
    }cout<<rs-s;
}
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