#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int nx=3e5+5;
ll n, s, vs[nx], c[nx], p, res, cur;
vector<ll> d[nx];
vector<pair<ll, ll>> dp[nx];
priority_queue<pair<ll, ll>> pq;
void dfs(int u, ll sm, ll mn, int rt)
{
vs[u]=1;
sm+=c[u];
if (sm>0)
{
dp[rt].push_back({sm, mn});
if (!d[u].empty()) dfs(d[u][0], 0, 0, rt);
}
else if (!d[u].empty()) dfs(d[u][0], sm, min(mn, sm), rt);
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>s;
cur=s;
for (int i=1; i<=n; i++)
{
cin>>c[i]>>p;
if (p!=0) d[p].push_back(i);
}
for (int i=1; i<=n; i++) if (!vs[i]) dfs(i, 0, 0, i);
for (int i=1; i<=n; i++) reverse(dp[i].begin(), dp[i].end());
for (int i=1; i<=n; i++) if (!dp[i].empty()) pq.push({dp[i].back().second, i});
while (!pq.empty())
{
auto [_, idx]=pq.top();
pq.pop();
if (-dp[idx].back().second>cur) break;
cur+=dp[idx].back().first;
dp[idx].pop_back();
if (!dp[idx].empty()) pq.push({dp[idx].back().second, idx});
}
cout<<cur-s;
}
