//
// Created by adavy on 8/18/2024.
//
#include <bits/stdc++.h>
//#pragma GCC optimize("O3")
using namespace std;
using ll = long long;
const ll MOD = 1e9 + 7;
#define int ll
#define f first
#define s second
pair<ll,ll> merge(pair<ll,ll> a, pair<ll,ll> b){
return {min(a.f,b.f),a.s-max(a.f,b.f)+b.s};
}
struct prs{
set<pair<ll,ll>> ps;
void insert(pair<ll,ll> p){
//cout << "ps: " << endl;
//for(auto& itm:ps){
// cout << itm.f << " " << itm.s << endl;
//}
//cout << "p: " << p.f << " " << p.s << endl;
while(1){
auto it = ps.lower_bound(p);
if (it != ps.end()) {
if (it-> f <= p.s){
p = merge(p,*it);
ps.erase(it);
continue;
}
}
auto it2 = ps.upper_bound(p);
if (it2 != ps.begin()){
--it2;
if (it2->s >= p.f){
p = merge(p,*it2);
ps.erase(it2);
continue;
}
}
ps.insert(p);
break;
}
}
void subtract(ll x){
ll balance = -x;
ll neg = balance;
while (!ps.empty() && balance < 0){
balance -= ps.begin()->f;
neg = min(neg,balance);
balance += ps.begin()->s;
ps.erase(ps.begin());
}
if (balance >= 0){
ps.insert({-neg,balance-neg});
}
}
};
vector<int> val;
vector<prs> sets;
vector<int> which;
vector<vector<int>> adj;
void iterative_dfs(int rt){
stack<pair<pair<int,int>,bool>> st;
st.push({{rt,-1},false});
while (!st.empty()){
auto [nds,stt] = st.top(); st.pop();
int v = nds.f, p = nds.s;
//if (v%1000 == 0) cout << "v: " << v << " p: " << p << " stt: " << stt << endl;
if (stt==0){
st.push({{v,p},true});
for(int u:adj[v]){
if (u == p) continue;
st.push({{u,v},false});
}
}
else{
int maxsz = -1, maxch = -1;
for(int u:adj[v]){
if (u == p) continue;
if (sets[u].ps.size() > maxsz){
maxsz = sets[u].ps.size();
maxch = u;
}
}
if (maxsz == -1){
which[v] = v;
}
else {
which[v] = which[maxch];
}
for(int u:adj[v]){
if (u==p || u == maxch) continue;
for(auto& itm:sets[u].ps){
sets[which[v]].insert(itm);
}
}
if (val[v] > 0){
sets[which[v]].insert({0LL,val[v]});
}
else {
sets[which[v]].subtract(-val[v]);
}
}
}
}
signed main(){
//freopen("input.txt","r",stdin);
std::ios::sync_with_stdio(false); cin.tie(NULL);
int N,s; cin >> N >> s;
adj.resize(N+5);
val.resize(N+1);
sets.resize(N+1);
which.resize(N+1,-1);
val[0] = 0;
for(int i=1;i<=N;++i){
ll x,p; cin >> x >> p;
val[i] = x;
adj[p].push_back(i);
adj[i].push_back(p);
}
iterative_dfs(0);
int t = s;
for(auto& item:sets[which[0]].ps){
if (t >= item.f){
t -= item.f;
t += item.s;
}
}
cout << t-s << endl;
}
