#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5;
vector<int> adj[N];
int dfs(int node, vector<pair<int, int>>& job, vector<bool>& vis) {
vis[node] = true;
int sum = job[node].first;
for (auto i : adj[node]) {
if (!vis[i]) {
sum += dfs(i, job, vis);
}
}
return sum;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, s;
cin >> n >> s;
vector<pair<int, int>> job(n);
for (int i = 0; i < n; ++i) {
cin >> job[i].first >> job[i].second;
if (job[i].second != 0) {
adj[i].push_back(job[i].second - 1);
}
}
vector<int> dp(n, 0);
vector<bool> vis(n, false);
dp[0] = max(job[0].first + s, s);
vis[0] = dp[0] == job[0].first + s;
for (int i = 1; i < n; ++i) {
if (job[i].second == 0) {
dp[i] = max(dp[i - 1], dp[i - 1] + job[i].first);
} else {
int parent = job[i].second - 1;
if (!vis[parent]) {
dp[i] = dp[i - 1] + dfs(parent, job, vis);
}
dp[i] = max(dp[i - 1], dp[i] + job[i].first);
}
vis[i] = dp[i] != dp[i - 1];
}
cout << dp[n - 1] - s << endl;
return 0;
}
