#include <bits/stdc++.h>
#define maxn 300005
#define fi first
#define se second
using namespace std;
using ii = pair<int, int>;
int n, root;
int c[maxn];
int64_t s[maxn], T, mint[maxn];
ii edges[maxn];
int cl[maxn], par[maxn];
vector<int> adj[maxn];
void pfs(int u) {
if (cl[u]) {
s[u] = 0;
mint[u] = LLONG_MAX;
}
else {
mint[u] = min(mint[u], s[u] += c[u]);
}
for (int v : adj[u]) {
s[v] = s[u];
mint[v] = mint[u];
pfs(v);
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> T;
int64_t old = T;
for (int i = 1; i <= n; i++) {
cin >> c[i] >> par[i];
adj[par[i]].emplace_back(i);
}
par[0] = -1;
for (int _ = 0; _ <= n; _++) {
s[0] = 0; mint[0] = LLONG_MAX;
pfs(0);
int p = -1;
int64_t mx = LLONG_MIN;
for (int i = 0; i <= n; i++) {
if (!cl[i] && s[i] >= 0 && -mint[i] <= T && mx < s[i]) {
mx = s[i];
p = i;
}
}
if (p == -1) break;
T += s[p];
while (p != -1) {
cl[p] = 1;
p = par[p];
}
}
cout << T - old;
}
/*
6 1
3 0
-3 1
-5 0
2 1
6 3
-4 5
6
*/
