#include <bits/stdc++.h>
#define maxn 300005
using namespace std;
int n;
int64_t s;
int c[maxn], p[maxn], start[maxn], stop[maxn], id = -1, euler[maxn];
int64_t sum[maxn], dp[maxn];
vector<int> adj[maxn];
void dfs(int u) {
start[u] = ++id;
euler[id] = u;
sum[u] += c[u];
for (int v : adj[u]) {
dfs(v);
sum[u] += sum[v];
}
stop[u] = id;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> s;
for (int i = 1; i <= n; i++) cin >> c[i] >> p[i];
for (int i = 1; i <= n; i++) adj[p[i]].emplace_back(i);
dfs(0);
int64_t ans = 0;
for (int i = 1; i <= n; i++) ans += c[i];
for (int i = n; i >= 0; i--) dp[i] = max(dp[stop[euler[i]]+1] - sum[euler[i]], dp[i+1]);
cout << ans + dp[0];
}
/*
6 1
3 0
-3 1
-5 0
2 1
6 3
-4 5
6
*/
