#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int long long
const ll INF = 2e18;
void DFS(int v, vector<vector<int>>& adj, vector<ll>& dp, vector<int>& x, ll minPre, ll currSum, int start){
currSum += x[v];
minPre = min(minPre, currSum);
if(currSum >= 0){
dp[start] = min(dp[start], -minPre);
}
for(int node : adj[v]){
DFS(node, adj, dp, x, minPre, currSum, start);
}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int N; ll s; cin >> N >> s;
ll orgs = s;
vector<int> x(N), p(N);
vector<vector<int>> adj(N);
for(int i = 0; i < N; i++){
cin >> x[i] >> p[i]; p[i]--;
if(p[i] != -1){
adj[p[i]].push_back(i);
}
}
vector<ll> dp(N, INF);
for(int i = 0; i < N; i++){
DFS(i, adj, dp, x, 0, 0, i);
}
priority_queue<pair<ll, int>> q;
for(int i = 0; i < N; i++){
if(p[i] == -1){
q.push({-dp[i], i});
}
}
while(!q.empty() && -q.top().first <= s){
int v = q.top().second; q.pop();
s += x[v];
for(int node : adj[v]){
q.push({-dp[node], node});
}
}
cout << s - orgs << "\n";
}
