#include <bits/stdc++.h>
#define pb push_back
#define int long long
using namespace std;
const int N = 3e5 + 5;
const int K = 20;
const int mod = 1e9 + 7;
vector<int> adj[N], x(N), p(N), gett(N);
vector<int> radj[N], lstadj[N];
void calc(int node, int lastpar){
if(x[node] >= 0){
gett[lastpar] += x[node];
for(auto itr: adj[node]){
calc(itr, lastpar);
}
}
else{
radj[lastpar].pb(node);
for(auto itr: adj[node]){
calc(itr, node);
}
}
}
void make_good(int node){
for(auto itr: radj[node]){
make_good(itr);
}
priority_queue<array<int, 2> > pq;
for(auto itr: radj[node]){
if(x[itr] <= gett[itr]) pq.push({-x[itr], itr});
}
int wh = gett[node] - x[node];
while(pq.size() && x[node] > gett[node]){
int cst = -pq.top()[0];
int u = pq.top()[1];
pq.pop();
x[node] = max(x[node], -(wh - cst));
gett[node] += (gett[u] - x[u]);
wh += (gett[u] - x[u]);
for(auto itr: lstadj[u]){
if(x[itr] <= gett[itr]) pq.push({-x[itr], itr});
}
}
if(x[node] <= gett[node]){
while(!pq.empty()){
int u = pq.top()[1];
if(x[u] <= gett[u]) lstadj[node].pb(u);
pq.pop();
}
}
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int n, s;
cin>>n>>s;
for(int i = 1; i <= n; i++){
cin>>x[i]>>p[i];
adj[p[i]].pb(i);
}
calc(0, 0); // suan bad ve good nodelar var öyle ki x[i] ödeyebiliyorsan get[i] kazanabiliyorsun
for(int i = 0; i <= n; i++) x[i] = -x[i]; // costa çevirdim
make_good(0);
int now = s;
priority_queue<pair<int, int> > pq;
pq.push({-x[0], 0});
while(pq.size()){
int u = pq.top().second;
pq.pop();
if(x[u] <= now && x[u] <= gett[u]){
now = (now - x[u] + gett[u]);
for(auto itr: lstadj[u]){
pq.push({-x[itr], itr});
}
}
}
cout<<now - s<<endl;
return 0;
}
