#include <bits/stdc++.h>
#define pb push_back
#define ll long long int
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
using namespace std;
vector<int> adj[300005];
vector<ll> pr(300005), memo(300005);
ll dp(int v) {
if (adj[v].size() == 0) {
if (pr[v] <= 0) return 0LL;
else return pr[v];
}
if (memo[v] != 0) {
return max(memo[v], 0LL);
}
ll sum = 0;
for (auto x : adj[v]) {
sum += dp(x);
}
memo[v] = max(sum+pr[v], -1LL);
return max(sum+pr[v], 0LL);
}
int main() {
int n; ll s; cin >> n >> s;
for (int i = 1; i <= n; i++) {
ll x; int p;
cin >> x >> p;
adj[p].pb(i);
pr[i] = x;
}
cout << dp(0);
return 0;
}
