#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
ll n,k;cin>>n>>k;
vector<pair<ll, ll>> A(n);
for(pair<ll, ll> &i:A) { cin>>i.first>>i.second; i.second--; }
vector<vector<ll>> childs(n);
vector<ll> roots;
for(ll i=0;i<n;i++){
if(A[i].second == -1){
roots.push_back(i);
continue;
}
childs[A[i].second].push_back(i);
}
ll res=0;
vector<ll> value(n);
vector<ll> prereq(n);
priority_queue<pair<ll, ll>> prereqs;
stack<ll> dfs;
for(ll r:roots) dfs.push(r);
while(!dfs.empty()){
ll c = dfs.top();
dfs.pop();
if(A[c].second == -1){
value[c] = A[c].first;
prereq[c] = min(0ll, A[c].first);
}
else{
value[c] = A[c].first + value[A[c].second];
prereq[c] = min(value[c], prereq[A[c].second]);
}
prereqs.push({prereq[c], c});
for(ll e:childs[c]){
dfs.push(e);
}
}
priority_queue<pair<ll, ll>> mxvals;
vector<bool> vis(n, false);
while(true){
while(!prereqs.empty() && prereqs.top().first + k >= 0){
mxvals.push({value[prereqs.top().second], prereqs.top().second});
prereqs.pop();
}
if(mxvals.empty()){
break;
}
ll cur = mxvals.top().second;
// cout << cur << '\n';
ll last = cur;
mxvals.pop();
ll oldk = k;
while(cur != -1 && !vis[cur]){
k += A[cur].first;
res += A[cur].first;
A[cur].first = 0;
vis[cur] = true;
cur = A[cur].second;
}
if(oldk > k){
A[last].first = k - oldk;
vis[last] = false;
res += oldk - k;
k = oldk;
}
}
cout << res << '\n';
}
