#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF 1e18
void solve() {
int n;
cin >> n;
vector<int> p(n + 1);
cin >> p[0];
vector<int> roots;
vector<queue<int>> a(n + 1);
multiset<pair<int, int>> st;
int curroot = 0;
for (int i = 1; i <= n; i++) {
int dep; cin >> p[i] >> dep;
if (dep == 0) {
roots.push_back(i);
curroot = i;
}
a[curroot].push(p[i]);
}
bool popped = true;
while (popped) {
popped = false;
for (int root : roots) {
if (a[root].empty()) continue;
int req = 0, sum = 0;
do {
// cout << "popping " << a[root].front() << " from " << root << "\n";
popped = true;
sum += a[root].front();
req = min(req, sum);
a[root].pop();
} while (!a[root].empty() && sum <= 0);
if (sum > 0) st.insert({-req, sum});
}
}
int ans = p[0];
for (auto [req, sum] : st) {
// cout << req << " " << sum << "\n";
if (ans >= req) {
ans += sum;
}
}
cout << ans - p[0];
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
return 0;
}
