#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int, int>
const int MAX_N = 3e5+1;
int N, S;
vector<vector<int>> ch;
vector<int> x;
struct merger{
vector<vector<pii>> groups;
priority_queue<pii> ev;
void add(vector<pii> vals){
int id = groups.size();
groups.push_back(vals);
if(vals.size()>0){
ev.push({vals.back().first, id});
}
}
bool empty(){
return ev.size()==0;
}
pii get(){
pii cords = ev.top();
ev.pop();
pii val = groups[cords.second].back();
groups[cords.second].pop_back();
if(groups[cords.second].size()>0){
ev.push({groups[cords.second].back().first, cords.second});
}
return val;
}
};
vector<pii> dfs(int i){
merger m;
for(auto e: ch[i]){
m.add(dfs(e));
}
vector<pii> ev;
while(!m.empty()){
ev.push_back(m.get());
}
reverse(ev.begin(), ev.end());
ev.push_back({x[i], x[i]});
while(ev.size()>1 && ev.back().second<0){
pii cur = ev.back();
ev.pop_back();
ev.back().second += cur.second;
ev.back().first = min(ev.back().first + cur.second, cur.first);
}
if(ev.back().second<0){
return {};
}
int cur_s = 0;
int cost = 0;
vector<pii> res;
while(ev.size()>0){
pii cur_stats= ev.back();
ev.pop_back();
if(cur_stats.first+cur_s>=0){
}
else{
cost += cur_stats.first+cur_s;
cur_s = -cur_stats.first;
}
cur_s += cur_stats.second;
res.push_back({cur_stats.first, cur_stats.second});
}
if(res.back().second<0){
return {};
}
reverse(res.begin(), res.end());
return res;
}
signed main(){
cin>>N>>S;
x.resize(N+1, 0);
ch.resize(N+1);
for(int i = 0; i<N; i++){
int p;
cin>>x[i+1]>>p;
ch[p].push_back(i+1);
}
auto ev = dfs(0);
int init_s= S;
while(ev.size()>0 && ev.back().first+S>=0){
S+= ev.back().second;
ev.pop_back();
}
cout<<S-init_s<<endl;
}
