#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define plx pair<ll,int>
#define f first
#define s second
#define pb push_back
#define all(x) x.begin(),x.end()
#define szz(r) (ll)r.size()
#define vi vector<int>
#define vvi vector<vi>
#define pp pair<ll,int>
#define ub(x,i) upper_bound(all(x),i)-x.begin()
using namespace std;
const int mxn=3e5+5;
vector<int>g[mxn];
ll x[mxn]{0};
multiset<pii>ms[mxn];
void dfs(int u){
for(auto v:g[u]){
dfs(v);
if(ms[u].size()<ms[v].size())swap(ms[u],ms[v]);
for(auto it:ms[v])ms[u].insert(it);
}
ll st=max(-x[u],1ll*0),pf=x[u];
if(st==0)ms[u].insert({st,pf});
else {
while(pf<0&&!ms[u].empty()){
auto it = ms[u].begin();
st = max(st,it->f-pf);
pf+=it->s;ms[u].erase(it);
}
if(pf>=0){
while(!ms[u].empty()){
auto it=ms[u].begin();
if(it->f<=st)pf+=it->s,ms[u].erase(it);
else break;
}ms[u].insert({st,pf});
}
}
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
ll n,s;cin>>n>>s;
for(int i=1;i<=n;i++){
int p;cin>>x[i]>>p;
g[p].pb(i);
}dfs(0);
ll rs=0;
for(auto it : ms[0])if(rs+s>=it.f)rs+=it.s;
cout<<rs;
}
