#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=3e5+10;
int n, s, p[N], x[N];
vector<int> g[N];
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq[N];
void dfs(int u){
for (int v:g[u]){
dfs(v);
if (pq[u].size()<pq[v].size()) pq[u].swap(pq[v]);
while (pq[v].size()) pq[u].push(pq[v].top()), pq[v].pop();
}
if (x[u]>=0) pq[u].emplace(0, x[u]);
else{
int need=-x[u], pf=-x[u];
while (need && pq[u].size()){
auto t=pq[u].top(); pq[u].pop();
int m=min(need, t.second);
pf=max(pf, need+t.first);
need-=m; t.second-=m;
if (t.second) pq[u].push(t);
}
if (need) return;
int sum=0;
while (pq[u].size() && pq[u].top().first<=pf){
sum+=pq[u].top().second;
pq[u].pop();
}
pq[u].emplace(pf, sum);
}
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> s;
for (int i=1; i<=n; ++i){
cin >> x[i] >> p[i];
g[p[i]].push_back(i);
}
dfs(0);
int cur=s;
while (pq[0].size() && cur>=pq[0].top().first){
cur+=pq[0].top().second;
pq[0].pop();
}
cout << cur-s << '\n';
return 0;
}
