#include <bits/stdc++.h> using namespace std; #define F first #define S second #define MP make_pair #define PB push_back #define all(x) begin(x), end(x) using ll = long long; using pi = pair<int, int>; using pll = pair<ll, ll>; using str = string; template<typename T> using vec = vector<T>; template<typename T, size_t N> using arr = array<T, N>; const ll INF = 1e17; const int MOD = 1e9 + 7; int N; ll s; vec<int> x, p; int main() { ios_base::sync_with_stdio(false); cin.tie(NULL); cin >> N >> s; x = p = vec<int>(N + 1); vec<int> v, nxt(N + 1); for (int i = 1; i <= N; i++) { cin >> x[i] >> p[i]; if (!p[i]) v.PB(i); else nxt[p[i]] = i; } ll ans = 0; for (int i : v) { ll res = 0, sum = 0; for (int j = i; j != 0; j = nxt[j]) { res = max(res, sum); sum += x[j]; } ans = max(ans, ans + res); } cout << ans << '\n'; }