#include <iostream>
#include <bits/extc++.h>
#define ll long long
using namespace std;
#define heap __gnu_pbds::priority_queue<int, cmp, __gnu_pbds::pairing_heap_tag>
const int MAXN = 3e5+5;
ll need[MAXN],sum[MAXN],val[MAXN];
vector<int> adj[MAXN];
struct cmp{
bool operator()(int x, int y){
return need[x] > need[y];
}
};
heap pq[MAXN];
void push(int u){
ll cur = 0; pq[u].push(u);
need[u] = 0;
//cout << u << "\n";
while(!pq[u].empty()){
int x = pq[u].top(); pq[u].pop();
//cout << x << " " << need[x] << "\n";
if(need[x] == 2e18) continue;
if(cur < need[x]){
need[u] += need[x]-cur;
cur = need[x];
}
if(x == u){
cur += val[u];
for(auto v : adj[u]){
pq[u].push(v);
}
}
else{
cur += sum[x];
if(pq[u].size() < pq[x].size()) pq[u].swap(pq[x]);
pq[u].join(pq[x]);
}
if(cur > need[u]){
sum[u] = cur-need[u];
//cout << u << " " << need[u] << "\n";
return;
}
}
need[u] = 2e18;
}
void dfs(int u){
for(auto v : adj[u]){
dfs(v);
}
push(u);
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N; ll S; cin >> N >> S;
for(int i = 1;i<=N;++i){ //add a node 0 to connect them all
cin >> val[i+1];
int p; cin >> p;
adj[p+1].push_back(i+1);
}
dfs(1);
heap q; ll cur = S;
q.push(1);
while(!q.empty()){
int u = q.top(); q.pop();
//cout << u << " " << need[u] << " " << val[u] << " " << cur << "\n";
if(cur < need[u]) break;
cur += val[u];
for(auto v : adj[u]){
q.push(v);
}
}
cout << cur-S << "\n";
return 0;
}
