#include <bits/stdc++.h>
#define pii pair<ll, ll>
typedef long long ll;
using namespace std;
const int MAX = 300003;
set<int> G[MAX];
priority_queue<pii, vector<pii>, greater<pii>> PQ[MAX];
pii S[MAX], off[MAX];
ll P[MAX];
void DFS(int cur) {
for (int next : G[cur]) DFS(next);
auto& [a, b] = S[cur];
while (!PQ[cur].empty()) {
auto [c, d] = PQ[cur].top();
c += off[cur].first; d += off[cur].second;
if (b < c) break;
if (c < d) b = b + d - c;
PQ[cur].pop();
}
if (!cur) return;
if (a < b) PQ[P[cur]].emplace(a - off[P[cur]].first, b - off[P[cur]].second);
off[cur].first += a - b;
off[cur].second += min(0LL, a - b);
if (PQ[cur].size() > PQ[P[cur]].size()) {
swap(off[cur], off[P[cur]]);
swap(PQ[cur], PQ[P[cur]]);
}
while (!PQ[cur].empty()) {
auto [c, d] = PQ[cur].top(); PQ[cur].pop();
c = c + off[cur].first; d += off[cur].second;
PQ[P[cur]].emplace(c - off[P[cur]].first, d - off[P[cur]].second);
}
// cout << "Current " << cur << ": " << a << ' ' << b << '\n';
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
ll N, IS;
cin >> N >> IS;
S[0] = {0, IS};
for (int i = 1; i <= N; ++i) {
ll s;
cin >> s >> P[i];
G[P[i]].insert(i);
if (s < 0) S[i] = {-s, 0};
else S[i] = {0, s};
}
DFS(0);
ll ans = S[0].second - IS;
cout << ans;
return 0;
}
