#include <bits/stdc++.h>
using namespace std;
long long INF = 2e18;
struct hyperDSU {
//dsu also contains pq
vector<int> par;
vector< priority_queue< pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> > PQ;
void init(int n) {
par.resize(n); PQ.resize(n);
while (n--) par[n] = n;
return;
}
int find(int u) {
if (par[u] == u) return u;
par[u] = find(par[u]);
return par[u];
}
void pushToPQ(pair<long long, int>& x, int u) {
u = find(u);
PQ[u].push(x);
return;
}
pair<long long, int> getPQTop(int u) {
u = find(u);
if (PQ[u].size() == 0) return {INF, 0};
return PQ[u].top();
}
void clearPQTop(int u) {
u = find(u);
if (PQ[u].size() == 0) return;
PQ[u].pop();
return;
}
bool join(int u, int v) {
u = find(u); v = find(v);
if (u == v) return false;
if (PQ[u].size() < PQ[v].size()) swap(u,v);
while (PQ[v].size()) {
PQ[u].push(PQ[v].top()); PQ[v].pop();
}
par[v] = u;
return true;
}
};
hyperDSU D;
vector<int> par;
vector<long long> A;
vector<pair<long long, long long>> dp; //dp ={min S required, advantage gain}
vector<vector<int>> E;
void dfs(int u) {
for (auto v: E[u]) {
dfs(v);
}
if (E[u].size() == 0) {
//cout << "huh " << u << "\n";
if (A[u] < 0) dp[u] = {INF, 0};
else dp[u] = {0, A[u]};
} else if (u != 0) {
for (auto v: E[u]) {
pair<long long, int> toAdd = {dp[v].first, v};
D.pushToPQ(toAdd, u);
}
long long curS = A[u], Av = 0, P = A[u]; //P = profit
if (curS < 0) {Av -= curS; curS = 0;}
while (P < 0) {
pair<long long, int> w = D.getPQTop(u);
if (w.first == INF) break;
D.clearPQTop(u);
//if it's too low to get the advantage, supply more
if (curS < w.first) {
Av += w.first-curS;
curS = w.first;
}
//apply the advantage
curS += dp[w.second].second;
P += dp[w.second].second;
//merge u's PQ with the added PQ
D.join(u, w.second);
}
if (P < 0) dp[u] = {INF, 0};
else dp[u] = {Av, P};
} else {
//final result calculation
for (auto v: E[u]) {
pair<long long, int> toAdd = {dp[v].first, v};
D.pushToPQ(toAdd, u);
}
long long curS = A[u];
while (true) {
pair<long long, int> w = D.getPQTop(u);
if (curS < w.first) break;
D.clearPQTop(u);
//apply the advantage
curS += dp[w.second].second;
//merge PQ
D.join(u, w.second);
}
dp[u] = {0, curS};
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int n,i; cin >> n;
A.resize(n+1); dp.resize(n+1); D.init(n+1); E.resize(n+1); par.resize(n+1, -1);
long long s; cin >> s;
A[0] = s;
i = 0; while (i++ < n) {
cin >> A[i] >> par[i];
E[par[i]].push_back(i);
}
dfs(0);
//for (auto x: dp) cout << x.first << " " << x.second << "a\n";
cout << dp[0].second-s;
return 0;
}
