#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define v vector
#define lp(i,s,e)for(ll i =s;i<e;++i)
struct st {
ll req, profit;
bool operator<(const st& other) const {
return req > other.req;
}
};
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n,s;
cin>>n>>s;
v<v<ll>> g(n);
v<ll> bef(n), pro(n);
lp(i,0,n) {
cin>>pro[i]>>bef[i];
bef[i]--;
}
lp(i,0,n) {
if (bef[i]!=-1)g[bef[i]].push_back(i);
}
v<st> after(n);
v<priority_queue<st, v<st>>> pq(n);
for (ll i = n-1;i>=0;--i) {
after[i].req= (pro[i]>0 ? 0: -pro[i]);
after[i].profit = pro[i];
for (auto it : g[i]) {
if (pq[i].size() < pq[it].size()) {
swap(pq[i], pq[it]);
}
while (!pq[it].empty()) {
pq[i].push(pq[it].top());
pq[it].pop();
}
}
while (!pq[i].empty()) {
auto [req,prof] = pq[i].top();
if (after[i].profit < 0 || after[i].req > req) {
pq[i].pop();
after[i].req = max(after[i].req, req-after[i].profit);
after[i].profit+=prof;
} else {
break;
}
}
if (after[i].profit > 0) {
pq[i].push(after[i]);
}
}
priority_queue<st, v<st>> final_pq;
lp(i,0,n) {
if (bef[i]==-1) {
while (!pq[i].empty()) {
final_pq.push(pq[i].top());
pq[i].pop();
}
}
}
ll cur = s;
ll ans = 0;
while (!final_pq.empty()) {
auto [req,prof] = final_pq.top();
final_pq.pop();
if (cur >= req) {
cur += prof;
ans += prof;
} else {
break;
}
}
cout<<ans<<'\n';
}
