#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// https://codeforces.com/blog/entry/79148
class Timer: chrono::high_resolution_clock {
const time_point start_time;
public:
Timer(): start_time(now()) {}
rep elapsed_time() const {
return chrono::duration_cast<chrono::milliseconds>(now() - start_time).count();
}
} timer;
int main() {
cin.tie(0);
ios::sync_with_stdio(0);
ll n, s;
cin >> n >> s;
ll ss = s;
vector<vector<ll>> graph(n);
vector<ll> x(n), p(n);
for (ll i = 0; i < n; i++) {
cin >> x[i] >> p[i];
p[i]--;
if (p[i] != -1) {
graph[p[i]].push_back(i);
}
}
// {low, net}
vector<pair<ll, ll>> res(n);
auto dfs = [&] (auto self, ll c, ll low, ll net)->void {
net += x[c];
low = min(low, net);
res[c] = {low, net};
for (auto &v : graph[c]) {
self(self, v, low, net);
}
};
for (ll i = 0; i < n; i++) {
if (p[i] == -1) {
dfs(dfs, i, 0, 0);
}
}
vector<bool> vis(n, 0);
while (true) {
ll best = 0, id = -1;
for (ll i = 0; i < n; i++) {
if (res[i].first + s >= 0 && res[i].second > best && !vis[i]) {
id = i;
best = res[i].second;
}
}
if (!best) {
break;
}
ll u = id;
stack<ll> stk;
stk.push(u);
while (p[u] != -1 && !vis[p[u]]) {
u = p[u];
stk.push(u);
}
while (stk.size()) {
u = stk.top();
stk.pop();
vis[u] = 1;
for (auto &v : graph[u]) {
if (stk.empty() || v != stk.top()) {
dfs(dfs, v, 0, 0);
}
}
s += x[u];
}
}
cout << s - ss;
return 0;
}
