#include <bits/stdc++.h>
using namespace std;
#define rep(a, b) for (int a = 0; a < (b); a++)
#define rep1(a, b) for (int a = 1; a <= (b); a++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int MOD = 1e9 + 7;
#define LOCAL false
const int LIM = 3e5 + 7;
int V;
ll s;
int vals[LIM];
vector<int> tree[LIM];
vector<int> roots;
ll calc(int v) {
ll tot = vals[v];
for (int to: tree[v]) tot += max(0LL, calc(to));
return max(0LL, tot);
}
void pod1() {
ll ans = 0;
for (int r: roots) ans += calc(r);
cout << ans << "\n";
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
if (LOCAL) {
ignore=freopen("io/in", "r", stdin);
ignore=freopen("io/out", "w", stdout);
}
cin >> V >> s;
int p;
rep1(v, V) {
cin >> vals[v] >> p;
if (p) tree[p].push_back(v);
else roots.push_back(v);
}
if (s == 1000000000000000000LL) {
pod1();
return 0;
}
return 0;
}
