#include <bits/stdc++.h>
using namespace std;
#define int long long
#define arr array
#define vec vector
#define pii pair<int, int>
#define fir first
#define sec second
const int N = 3e5 + 5, INF = 5e18;
int n, s;
arr<int, N> vl;
arr<vec<int>, N> ch;
void mrg(set<pii>& x, set<pii>& y) { // y into x
if (x.size() < y.size()) x.swap(y);
for (pii z : y) x.insert(z);
}
arr<set<pii>, N> dp;
void dfs(int u = 0) {
for (int v : ch[u]) {
dfs(v);
mrg(dp[u], dp[v]);
}
pii x = {max(-vl[u], 0ll), vl[u]};
while (dp[u].size() && (x.sec <= 0 || x >= *dp[u].begin())) {
pii y = *dp[u].begin(); dp[u].erase(dp[u].begin());
x = {max(x.fir, y.fir - x.sec), x.sec + y.sec};
}
if (x.sec <= 0) return;
dp[u].insert(x);
}
void cmp() {
int t = s;
for (pii x : dp[0]) {
if (t < x.fir) continue;
t += x.sec;
}
cout << t - s << '\n';
}
signed main() {
// freopen("in", "r", stdin);
cin >> n >> s;
for (int u = 1; u <= n; u++) {
int v; cin >> vl[u] >> v;
ch[v].push_back(u);
}
dfs();
// for (pii x : dp[0]) {
// cout << x.fir << " " << x.sec << '\n';
// }
cmp();
}
