#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;
arr<int, N> dp;
void dfs(int u = 0) {
for (int v : ch[u]) dfs(v);
if (vl[u] >= 0) return;
set<pii> ord;
for (int v : ch[u]) ord.insert({dp[v], v});
int st = -vl[u], cr = 0;
while (ord.size() && st > cr) {
int v = ord.begin()->sec; ord.erase(ord.begin());
if (dp[v] == INF) continue;
if (cr < dp[v]) {
int df = dp[v] - cr;
st += df, cr += df;
}
cr += vl[v];
for (int w : ch[v]) ord.insert({dp[w], w});
}
dp[u] = (st > cr) ? INF : st;
}
void cmp() {
set<pii> ord = {{dp[0], 0}};
int t = s;
while (ord.size()) {
int u = ord.begin()->sec; ord.erase(ord.begin());
if (dp[u] > t) continue;
t += vl[u];
for (int v : ch[u]) ord.insert({dp[v], v});
}
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 (int u = 1; u <= n; u++)
// cout << u << ": " << dp[u] << '\n';
cmp();
}
