#include<bits/stdc++.h>
using namespace std;
struct node {
node* p;
long long x,m=-1;
vector<node*> l, sub;
bool v = false;
};
void dfs(node* n, long long t, long long mi, set<pair<int, node*>>& s){
n->sub.clear();
n->sub.push_back(n);
t += n->x;
mi = min(mi, t);
if(t > 0){
s.insert({-mi, n});
n->m = -mi;
return;
}
for(node* c : n->l){
if(c->v) continue;
dfs(c, t, mi, s);
for(node* x : c->sub) n->sub.push_back(x);
}
}
void solve(){
int n;cin >> n;
long long s;cin >> s;
long long os = s;
node g[n+1];
for(int i = 1;i <= n;i++){
int p;
cin >> g[i].x >> p;
g[p].l.push_back(&g[i]);
g[i].p = &g[p];
}
set<pair<int, node*>> se;
g[0].x=0;
dfs(&g[0], 0, 0, se);
g[0].v=true;
while(!se.empty() && se.begin()->first <= s){
node* u = se.begin()->second;
se.erase(se.begin());
while(!u->v){
u->v=true;
s += u->x;
u->m = -1;
for(node* j : u->l) if(!j->v) {
for(node* c : j->sub) if(c->m != -1) {
se.erase({c->m,c});
c->m=-1;
}
dfs(j,0,0,se);
}
u=u->p;
}
}
cout << s-os << '\n';
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
}
