#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
#define pb push_back
#define ff first
#define ss second
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n; ll s; cin>>n>>s;
vector<int> g[n + 1], a(n + 1), p(n + 1);
for (int i = 1; i <= n; i++){
cin>>a[i]>>p[i];
g[p[i]].pb(i);
}
vector<ll> dp(n + 1);
function<void(int, int)> dfs = [&](int v, int pr){
dp[v] = a[v];
for (int i: g[v]){
if (i == pr) continue;
dfs(i, v);
dp[v] += dp[i];
}
dp[v] = max(dp[v], 0LL);
};
dfs(0, 0);
cout<<dp[0]<<"\n";
}
