#include<bits/stdc++.h>
using namespace std;
#define sz(v) (int)v.size()
#define all(v) begin(v), end(v)
#define compact(v) v.erase(unique(all(v)), end(v))
#define dbg(v) "[" #v " = " << (v) << "]"
#define file(name) if(fopen(name".inp", "r")) {freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
#define rep(i, l, r) for(int i = (l); i < (r); ++i)
using ll = long long;
using vi = vector<int>;
using vl = vector<long long>;
using ld = long double;
template<typename T>
bool minimize(T& a, const T& b){
if(a > b){
return a = b, true;
} return false;
}
template<typename T>
bool maximize(T& a, const T& b){
if(a < b){
return a = b, true;
} return false;
}
template<int dimension, typename T>
struct tensor : public vector<tensor<dimension - 1, T>> {
static_assert(dimension > 0, "Dimension must be positive !\n");
template<typename... Args>
tensor(int n = 0, Args... args) : vector<tensor<dimension - 1, T>> (n, tensor<dimension - 1, T>(args...)) {}
};
template<typename T>
struct tensor<1, T> : public vector<T> {
tensor(int n = 0, T val = T()) : vector<T>(n, val) {}
};
const int MAX = 3e5 + 5;
int n, x[MAX], p[MAX];
ll s;
vector<int> adj[MAX];
priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> pq[MAX];
void insert(auto& pq, pair<ll, ll> nw){
while(!pq.empty()){
pair<ll, ll> tp = pq.top();
if(nw.second <= 0){
pq.pop();
nw = {max(nw.first, tp.first - nw.second), nw.second + tp.second};
} else{
if(nw.first > tp.first){
pq.pop();
nw = {nw.first, nw.second + tp.second};
} else{
pq.push(nw);
break;
}
}
}
if(pq.empty()) pq.push(nw);
while(!pq.empty() && pq.top().second <= 0) pq.pop();
}
void dfs(int u){
for(int v : adj[u]){
dfs(v);
if(sz(pq[u]) < sz(pq[v])){
swap(pq[u], pq[v]);
}
while(!pq[v].empty()){
pq[u].push(pq[v].top());
pq[v].pop();
}
}
insert(pq[u], {max(0ll, -1ll * x[u]), x[u]});
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
if(fopen("task.inp", "r")){
freopen("task.inp", "r", stdin);
freopen("task.out", "w", stdout);
}
cin >> n >> s;
for(int i = 1; i <= n; ++i){
cin >> x[i] >> p[i];
adj[p[i]].push_back(i);
}
dfs(0);
ll profit = 0;
while(!pq[0].empty() && s + profit >= pq[0].top().first){
profit += pq[0].top().second; pq[0].pop();
}
cout << profit << '\n';
return 0;
}
