#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl;
#define show4(x,y) for(auto it:y) cout << it << " "; cout << #x << endl;
typedef pair<int,int>pii;
typedef pair<int,pii>pi2;
vector<int>adj[300005];
int arr[300005];
multiset<pii>se[300005];
void dfs(int index){
for(auto it:adj[index]){
dfs(it);
if(se[index].size()<se[it].size()) swap(se[index],se[it]);
for(auto ii:se[it]) se[index].insert(ii);
}
//big small
int counter=arr[index];
int need=max(0LL,-arr[index]);
while(counter<0){
if(se[index].empty()) break;
//greedily take the smallest
pii hold=*se[index].begin();
se[index].erase(se[index].find(hold));
need=max(need,-counter+hold.first);
counter+=hold.second;
}
if(counter>=0){
//consuming
while(!se[index].empty()&&se[index].begin()->first<need){
counter+=se[index].begin()->second;
se[index].erase(se[index].find(*se[index].begin()));
}
se[index].insert({need,counter});
}
}
void solve(){
int n,m;
cin >> n >> m;
int temp,temp2;
for(int x=1;x<=n;x++){
cin >> temp >> temp2;
arr[x]=temp;
adj[temp2].push_back(x);
}
arr[0]=0;
dfs(0);
int cur=m;
for(auto it:se[0]){
//assert(it.second>=0);
if(cur>=it.first) cur+=it.second;
}
cout << cur-m;
}
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0);
int t=1;
//cin >> t;
//freopen("in.txt","r",stdin);
while(t--){
solve();
}
}
