#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll inf = 1e18;
const int N = 3e5+10;
int n, p[N];
ll s, x[N];
vector<int> child[N];
ll dfs(int v)
{
for(int c : child[v])
x[v] += dfs(c);
return max(x[v], 0ll);
}
void subtask1()
{
cout << dfs(0) << endl;
exit(0);
}
int main()
{
cin >> n >> s;
for(int i = 1; i <= n; i ++)
{
cin >> x[i] >> p[i];
child[p[i]].push_back(i);
}
if(s == inf) subtask1();
set<pair<ll, int> > st;
for(int i = 1; i <= n; i ++)
if(p[i] == 0) st.insert({x[i], i});
ll init = s;
while(st.size())
{
int v = st.rbegin()->second;
st.erase(--st.end());
if(s + x[v] >= 0)
{
if(child[v].empty())
s += max(0ll, x[v]);
else
{
int c = child[v][0];
if(x[v] >= 0) s += x[v];
else x[c] += x[v];
st.insert({x[c], c});
}
}
}
cout << s - init << endl;
return 0;
}
