#include "bits/stdc++.h"
using namespace std;
#ifdef Nero
#include "Deb.h"
#else
#define debug(...)
#endif
const int N = 3e5 + 5;
int up[N];
int dep[N];
int a[N], p[N];
set<int> roots;
long long dp[N];
vector<int> g[N];
long long needed[N];
int get(int v) {
return (v == 0 ? 0 : dp[v] <= 0 ? v : up[v] = get(up[v]));
}
void dfs(int v, long long sum) {
sum += a[v];
needed[v] = min(needed[v], sum);
for (int u : g[v]) {
dep[u] = dep[v] + 1;
needed[u] = needed[v];
dfs(u, sum);
}
}
void activate(int v) {
dp[v] += a[v];
//debug(v);
while (true) {
//debug(v, dp[v]);
if (v == 0 || dp[v] <= 0) {
//cout << '\n';
return;
}
if (p[v] == 0 && dp[v] > 0) {
roots.insert(v);
}
int nv = get(v);
dp[nv] += dp[v];
v = nv;
}
//cout << '\n';
}
void dfs2(int v, long long& s) {
s += a[v];
for (int u : g[v]) {
if (dp[u] > 0) {
dfs2(u, s);
} else {
p[u] = 0;//new root.
}
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
long long s;
cin >> n >> s;
for (int i = 1; i <= n; ++i) {
cin >> a[i] >> p[i];
g[p[i]].push_back(i);
}
for (int i = 1; i <= n; ++i) {
up[i] = p[i];
if (p[i] == 0) {
dfs(i, 0);
}
}
vector<int> ord(n);
iota(ord.begin(), ord.end(), 1);
sort(ord.begin(), ord.end(), [&](int i, int j) {
return (needed[i] == needed[j] ? dep[i] > dep[j] : needed[i] < needed[j]);
});
long long curr = s;
while (true) {
while (!ord.empty() && -needed[ord.back()] <= curr) {
int v = ord.back();
ord.pop_back();
activate(v);
}
if (roots.empty()) {
break;
}
//debug(roots);
while (!roots.empty()) {
int v = *roots.begin();
roots.erase(v);
dfs2(v, curr);
}
}
cout << curr - s << '\n';
return 0;
}
