#include <bits/stdc++.h>
using namespace std;
using ll = long long; using pii = pair<ll,ll>;
const ll Nm = 3e5+5;
map<ll,ll> m0[Nm];
ll fz(ll a, ll b) {
if (a==-1) {
return b;
}
if (b==-1) {
return a;
}
if (m0[a].size()>m0[b].size()) {
swap(a,b);
}
for (pii p0: m0[a]) {
m0[b][p0.first]+=p0.second;
}
//cout << "fusing, returning b="<<b<<"\n";
return b;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
ll N,S; cin >> N >> S;
ll x[N]; ll p[N];
vector<ll> fadj[N];
vector<ll> fadjZ; //fadj zero
ll madd[N]; //memory address
for (ll i=0;i<N;i++) {
cin >> x[i] >> p[i];
madd[i]=i;
p[i]--;
if (p[i]==-1) {
fadjZ.push_back(i);
} else {
fadj[p[i]].push_back(i);
}
}
for (ll y=(N-1);y>=0;y--) {
for (ll z: fadj[y]) {
madd[y]=fz(madd[y],madd[z]);
}
ll A = madd[y];
if (x[y]>=0) {
m0[A][0]+=x[y];
} else {
vector<ll> delc; //delete coordinates
ll val = -x[y]; //negative of value
ll ov = -x[y]; //current overheard
while (!m0[A].empty() && val>0) {
auto A0 = m0[A].begin();
pii pstr = *A0; //{operation overhead, additional value}
m0[A].erase(A0);
ov = max(ov,pstr.first+val);
val = val - pstr.second;
}
if (val<=0) {
m0[A][ov]+=(-val);
}
}
}
ll A= -1;
for (ll y: fadjZ) {
A = fz(A,madd[y]);
}
ll S0 = S;
while (!m0[A].empty()) {
auto A0 = m0[A].begin();
pii p0 = *A0;
m0[A].erase(A0);
if (S>=p0.first) {
S += p0.second;
} else {
break;
}
}
cout << (S-S0) << "\n";
}
