#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
const int N = 3e5;
int n;
int a[N + 5], parent[N + 5];
priority_queue<pair<int,int>> pq[N + 5];
vector<int> con[N + 5];
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];
}
