// Author: Teoman Ata Korkmaz
#include <bits/stdc++.h>
#define int int_fast64_t
using namespace std;
constexpr int N=300005;
///////////////////////////////////////////////////////////
int n,k,x,p[N],c[N];
vector<tuple<int,int>> adj[N];
vector<vector<pair<int,int>>> v;
signed main(void){
cin>>n>>k;
const int K=k;
for(int i=0;i<n;i++){
cin>>c[i]>>p[i];p[i]--;
if(p[i]!=-1)adj[p[i]].push_back({i,c[i]});
}
for(int i=0;i<n;i++){
if(p[i]==-1)v.push_back({{0,c[i]}});
else v.back().push_back({0,c[i]});
}
// for(auto _:v){
// cerr<<"v:";
// for(auto i:_)cerr<<"["<<i.first<<","<<i.second<<"],";
// cerr<<endl;
// }
// cerr<<endl;
for(auto& v:v){
vector<pair<int,int>> t;
for(auto i:v){
if(t.size() && t.back().second<0){
t.back().second+=i.second;
}
else{
t.push_back(i);
}
t.back().first=min(t.back().second,t.back().first);
}
v=t;
}
// for(auto _:v){
// cerr<<"v:";
// for(auto i:_)cerr<<"["<<i.first<<","<<i.second<<"],";
// cerr<<endl;
// }
// cerr<<endl;
int ans=0;
priority_queue<tuple<int,int,int,int>> q;
for(int i=0;i<v.size();i++)q.push({v[i][0].first,v[i][0].second,i,0});
while(q.size()){
auto [x,y,i,j]=q.top();q.pop();
if(y<0 || x>k)continue;
k+=y;
ans=max(ans,k-K);
if(j+1<v[i].size())q.push({v[i][j+1].first,v[i][j+1].second,i,j});
}
cout<<ans<<endl;
}
