#include <bits/stdc++.h>
#define int long long
using namespace std;
const int inf = 1e18, nmax = 1e5;
set<pair<int, int>> con[nmax];
vector<int> adj[nmax];
int v[nmax];
void dfs(int i) {
for (auto it : adj[i]) {
dfs(it);
if (con[it].size() > con[i].size()) {
swap(con[i], con[it]);
}
for (auto it : con[it]) {
con[i].insert(it);
}
con[it].clear();
}
pair<int, int> tp = {min(0ll, v[i]), v[i]};
vector<pair<int, int>> des;
for (auto it : con[i]) {
if (tp.second > 0) {
break;
}
tp = {max(tp.first, it.first - tp.second), tp.second + it.second};
des.push_back(it);
}
for (auto it : des) {
con[i].erase(it);
}
if (tp.second <= 0) {
return;
}
if (con[i].size() == 0) {
con[i].insert(tp);
return;
}
des.clear();
for (auto it : con[i]) {
if (it.first <= tp.first) {
tp.second += it.second;
des.push_back(it);
} else {
break;
}
}
for (auto it : des) {
con[i].erase(it);
}
con[i].insert(tp);
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, s;
cin >> n >> s;
for (int i = 1; i < n; i++) {
int tata;
cin >> v[i] >> tata;
adj[tata].push_back(i);
}
dfs(0);
int xtra = 0;
for (auto it : con[0]) {
if (s + xtra >= it.first) {
xtra += it.second;
}
}
cout << xtra;
return 0;
}
