#include <bits/stdc++.h>
using namespace std;
#define rall(x) (x).rbegin(), (x).rend()
typedef long long ll;
vector<ll> profit;
vector<vector<ll>> children;
vector<pair<ll, ll>> res;
const ll z = 0ll;
ll non_neg(ll x) {
return max(x, z);
}
ll profit_dp(ll node) {
// profit = sum of (positive) profits of children
// return max(profit[node] + childrens_profit, 0)
ll sum = 0;
for(auto child: children[node]) sum += non_neg(profit_dp(child));
return non_neg(profit[node] + sum);
}
void dp(ll node, ll p, ll hi, ll lo) {
p += profit[node];
if(p > hi) res.push_back({lo - hi, p - hi});
for(auto child: children[node]) dp(child, p, max(hi, p), min(lo, p));
}
void solve() {
ll n, s;
cin >> n >> s;
profit.resize(n + 1);
children.resize(n + 1);
for(ll i = 0; i < n; i++){
int x, p;
cin >> x >> p;
profit[i+1] = x;
children[p].push_back(i+1);
}
if(s == 1000000000000000000ll) return (void)(cout << profit_dp(0));
for(auto start: children[0]) dp(start, z, z, z);
sort(rall(res));
ll a = 0;
for(auto r: res){
if (r.first + s < 0) break;
s += r.second;
a += r.second;
}
cout << a;
}
int main() {solve(); cout << endl;}
