#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;
vector<pii> dfs(int i){
vector<pii> res;
priority_queue<pii> ev;
vector<vector<pii>> ch_res;
for(auto e: ch[i]){
ch_res.push_back(dfs(e));
if(ch_res.back().size()>0){
ev.push({ch_res.back().back().first, ch_res.size()-1});
}
}
int cur_s = x[i];
int cost = 0;
while(ev.size()>0){
pii cur_ev = ev.top();
pii cur_stats= ch_res[cur_ev.second].back();
ch_res[cur_ev.second].pop_back();
ev.pop();
if(ch_res[cur_ev.second].size()>0){
ev.push({ch_res[cur_ev.second].back().first,cur_ev.second});
}
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({cost, cur_stats.second});
}
sort(res.begin(), res.end());
if(x[i]>=0){
res.push_back({0, 0});
}
if(res.size()>0){
res.back().first = min(x[i], res.back().first+x[i]);
res.back().second +=x[i];
}
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+init_s>=0){
S+= ev.back().second;
ev.pop_back();
}
cout<<S-init_s<<endl;
}
