#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
using ll = long long;
int N, x[300005], p[300005];
ll s, os, wei[300005], mn[300005];
bool seen[300005];
vector<int> adj[300005];
void dfs(int u) {
wei[u] += x[u];
mn[u] = min(mn[u], wei[u]);
for (auto v : adj[u]) {
wei[v] = wei[u];
mn[v] = min(mn[v], mn[u]);
dfs(v);
}
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> N >> s;
os = s;
for (int i = 1; i <= N; i++) {
cin >> x[i] >> p[i];
adj[p[i]].pb(i);
}
seen[0] = 1;
while (1) {
for (int i = 1; i <= N; i++) {
mn[i] = 0;
}
dfs(0);
pair<ll, int> tk = mp(-1, -1);
for (int i = 1; i <= N; i++) {
if (!seen[i] && s + mn[i] >= 0) {
tk = max(tk, mp(wei[i], i));
}
}
if (tk.first < 0) {
break;
}
s += tk.first;
for (int j = tk.second; !seen[j]; j = p[j]) {
seen[j] = 1;
x[j] = 0;
}
}
cout << s - os << '\n';
}
