#include <bits/stdc++.h>
using namespace std;
#define int long long
int n;
int a[300005],parent[300005];
priority_queue<pair<int,int>> pq[300005];//{negativ,profit}
vector<int> con[300005];
void dfs(int nod)
{
for(int adj:con[nod])
{
dfs(adj);
if((int)pq[nod].size() < (int)pq[adj].size())
swap(pq[nod], pq[adj]);
while(!pq[adj].empty())
{
pq[nod].push(pq[adj].top());
pq[adj].pop();
}
}
if(a[nod]>=0)
{
pq[nod].push({0,a[nod]});
}
else
{
pair<int,int> cur = {a[nod],a[nod]};
while(!pq[nod].empty() && cur.second<0)
{
pair<int,int> aux = pq[nod].top();
pq[nod].pop();
cur.first = min(cur.first, cur.second + aux.first);
cur.second += aux.second;
}
if(cur.second>=0)
{
while(!pq[nod].empty() && pq[nod].top().first >= cur.first)
{
cur.second += pq[nod].top().second;
pq[nod].pop();
}
pq[nod].push(cur);
}
}
}
signed main()
{
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n>>a[0];
for(int i=1;i<=n;i++)
{
cin>>a[i]>>parent[i];
con[parent[i]].push_back(i);
}
dfs(0);
int sum=0;
while(!pq[0].empty() && pq[0].top().first+sum>=0)
{
sum += pq[0].top().second;
pq[0].pop();
}
cout<<sum-a[0];
return 0;
}
