///~~~LOTA~~~///
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define append push_back
#define add insert
#define nl '\n'
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<ll,ll>
#define all(x) (x).begin(),(x).end()
#define L0TA ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define terminator main
#define N 300001
ll x[N];
ll y[N];
ll p[N];
ll dp[N];
ll val[N];
vector<int> a[N];
void dfs(int v){
dp[v]=val[v];
for(auto& i:a[v]){
dfs(i);
dp[v]+=dp[i];
}
dp[v]=max(dp[v],0LL);
}
void solve(){
ll n,m,s;
cin>>n>>s;
vector<pll> v;
for(int i=1;i<=n;i++){
cin>>val[i]>>p[i];
a[p[i]].append(i);
m=val[i];
if(x[p[i]]<0){
y[i]=max(y[p[i]],-x[p[i]]-m);
x[i]=x[p[i]]+m;
}
else{
x[i]=m;
y[i]=max(-m,y[p[i]]);
}
if(x[i]>0)
v.append({y[i],x[i]});
}
m=1e18;
if(s==m){
dfs(0);
cout<<dp[0];
return;
}
m=s;
sort(all(v));
for(auto& i:v){
if(i.ff>m) break;
m+=i.ss;
}
cout<<m-s;
}
int terminator(){
L0TA;
solve();
return 0;
}
