#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define ppb pop_back
#define ep insert
#define endl '\n'
#define elif else if
#define pow pwr
#define sqrt sqrtt
#define int long long
#define ll long long
#define y1 YONE
typedef unsigned long long ull;
using namespace std;
const int N=3e5+5;
int a[N],n,dp[N];
vector<int> adj[N];
int dfs(int x){
dp[x]=a[x];
for (auto u:adj[x]) dp[x]+=dfs(u);
if (dp[x]<0) dp[x]=0;
return dp[x];
}
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
cin>>n>>a[0];
for (int i=1;i<=n;i++){
cin>>a[i];
int p;cin>>p;
adj[p].pb(i);
}
cout<<dfs(0);
//for (int i=0;i<=n;i++) cout<<dp[i]<<' ';cout<<endl;
return 0;
}
