#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define f first
#define s second
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (ll)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 3e5 + 10;
vector <int> ed[N];
priority_queue <pair <ll, ll>> pq[N];
ll a[N];
void dfs(int u) {
for (auto x : ed[u]) {
dfs(x);
if (sz(pq[x]) > sz(pq[u]))
swap(pq[x], pq[u]);
while (sz(pq[x])) {
auto t = pq[x].top();
pq[x].pop();
pq[u].push(t);
}
}
if (a[u] > 0) {
pq[u].push({0, a[u]});
} else {
ll mn = a[u], sum = a[u];
while (sz(pq[u])) {
auto t = pq[u].top();
if (sum <= 0) {
mn = min(mn, sum + t.f);
sum += t.s;
pq[u].pop();
} else {
if (t.f < mn)
break;
sum += t.s;
pq[u].pop();
}
}
if (sum > 0)
pq[u].push({mn, sum});
}
}
ll solve() {
int n;
cin >> n >> a[0];
for (int i = 1; i <= n; i++) {
int x;
cin >> a[i] >> x;
ed[x].pb(i);
}
ll s = 0;
dfs(0);
while (sz(pq[0])) {
auto t = pq[0].top();
pq[0].pop();
if (s + t.f >= 0) {
s += t.s;
} else {
break;
}
}
return s - a[0];
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) {
cout << solve() << '\n';
}
return 0;
}
