#include<bits/stdc++.h>
#define int long long
#define MAXN (int)3e5+5
#define pq priority_queue
using namespace std;
#define ti tuple<int,int,int>
vector<int>g[MAXN];
pq<ti>p[MAXN];
int a[MAXN],m[MAXN];
//malo do veliko mesanje?!?!?!?!??!?!?!?!?!
pq<ti> merge(pq<ti>p1, pq<ti>p2){
if(p1.size()>p2.size()){
swap(p1,p2);
}while(!p1.empty()){
p2.push(p1.top());
p1.pop();
}
return p2;
}
int ps(int u){
while(!p[u].empty()){
int d,b,c;
tie(d,b,c)=p[u].top();p[u].pop();
if(-d>m[u]){
break;
}
if(g[b].size()>1){
m[b]=m[u]+c;
int x=ps(b);
if(m[b]>=m[u]){
m[u]=m[b];
p[u]=merge(p[u],p[b]);
continue;
}
p[u].emplace(x-c,b,c);
continue;
}
if(c>-1){
m[u]+=c;
d=0,c=0;
}
for(int&x:g[b]){
p[u].emplace(min(d,c+a[x]),x,c+a[x]);
}
}
if(!p[u].empty()){
int d,b,c;
tie(d,b,c)=p[u].top();
return d;
}
return -(int)2e18;
}
void solve() {
int n,s;cin>>n>>s;
for(int i=1;i<=n;i++){
int u;cin>>a[i]>>u;
g[u].push_back(i);
m[i]=-1;
}for(int i=0;i<=n;i++){
for(int&x:g[i]){
p[i].emplace(min(0ll,a[x]),x,a[x]);
}
}
m[0]=s;
ps(0);
cout<<m[0]-s<<'\n';
}
int32_t main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int32_t T=1;//cin>>T;
while(T--) {
solve();
}
return 0;
}
