#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ll2 = pair<ll, ll>;
int main() {
int n;
ll s;
cin >> n >> s;
n += 1;
vector<ll> x(n);
vector<vector<int>> g(n);
x[0] = 0;
for (int i = 1; i < n; ++i) {
int p;
cin >> x[i] >> p;
g[p].push_back(i);
}
vector<priority_queue<ll2, vector<ll2>, greater<ll2>>> pqs(n);
auto merge = [&](auto &pq1, auto &pq2) {
if (int(pq1.size()) < int(pq2.size())) {
swap(pq1, pq2);
}
while (not pq2.empty()) {
pq1.push(pq2.top());
pq2.pop();
}
};
auto dfs = [&](auto &&self, int v) -> void {
auto &pq = pqs[v];
for (int t : g[v]) {
self(self, t);
merge(pq, pqs[t]);
}
if (x[v] > 0) {
pq.push(make_pair(0ll, x[v]));
} else if (not pq.empty()) {
ll req = -x[v];
ll prf = x[v];
while (prf <= 0 and !pq.empty()) {
auto [r, p] = pq.top();
pq.pop();
req = max(req, -prf + r);
prf += p;
}
if (prf > 0) {
while (!pq.empty() and pq.top().first <= req) {
prf += pq.top().second;
pq.pop();
}
pq.push(make_pair(req, prf));
}
}
};
dfs(dfs, 0);
ll prf = 0;
auto &pq = pqs[0];
while (!pq.empty()) {
auto [r, p] = pq.top();
pq.pop();
if (r <= prf + s) {
prf += p;
}
}
cout << prf << endl;
}
