#include<iostream>
#include<vector>
#include<queue>
//#include<functional>
using namespace std;
int find(vector<int>& U, int a) {
while (a != U[a])
a = U[a];
return a;
}
// find + two pass path compression
int find2(vector<int>& U, int a) {
int root = a;
while (root != U[root])
root = U[root];
int next = U[a];
while (next != root) {
U[a] = root;
a = next;
next = U[a];
}
return root;
}
// merges roots only
void merge(vector<int>& U, int a, int b) {
U[find(U,b)] = find(U, a);
}
int main() {
int N, s;
cin >> N >> s;
vector<long long> x(N + 1);
vector<int> p(N + 1);
vector<long long> cost_to_take(N + 1);
vector<int> U(N + 1);
for (int i = 0;i < N + 1;++i) {
U[i] = i;
}
auto cmp = [&](int a, int b) {return cost_to_take[a] > cost_to_take[b];}; // least expensive jobs first
priority_queue<int, std::vector<int>, decltype(cmp)> pq(cmp);
x[0] = s;
p[0] = 0;
for (int i = 1;i < N + 1; ++i) {
cin >> x[i] >> p[i];
if (x[i] < 0) {
cost_to_take[i] = -x[i];
}
else {
pq.push(i);
}
}
while (!pq.empty()) {
int least_expensive_job = pq.top(); // least expensive job
pq.pop();
int least_expensive_job_parent = find2(U, p[least_expensive_job]); // least expensive job parent
if (cost_to_take[least_expensive_job_parent] + x[least_expensive_job_parent] >= cost_to_take[least_expensive_job]) {
merge(U, least_expensive_job_parent, least_expensive_job); // merge jobs
x[least_expensive_job_parent] += x[least_expensive_job]; // add profits
x[least_expensive_job] = 0;
//cout << 'a' << ' ' << least_expensive_job << ' ' << least_expensive_job_parent << ' ' << cost_to_take[least_expensive_job_parent] << ' ' << x[least_expensive_job_parent] << ' ' << x[0] << endl;
}
else {
//cout << 'b' << ' ' << least_expensive_job << ' ' << least_expensive_job_parent << ' ' << cost_to_take[least_expensive_job_parent] << ' ' << x[least_expensive_job_parent] << ' ' << x[0] << endl;
if (least_expensive_job_parent != 0) {
merge(U, least_expensive_job_parent, least_expensive_job); // merge jobs
cost_to_take[least_expensive_job_parent] = cost_to_take[least_expensive_job] - x[least_expensive_job_parent];
x[least_expensive_job_parent] += x[least_expensive_job]; // add profits
x[least_expensive_job] = 0;
//cout << 'b' << ' ' << least_expensive_job << ' ' << least_expensive_job_parent << ' ' << cost_to_take[least_expensive_job_parent] << ' ' << x[least_expensive_job_parent] << endl;
}
}
if (least_expensive_job_parent != 0 && x[least_expensive_job_parent] > 0) {
//cout << 'c' << ' ' << least_expensive_job << ' ' << least_expensive_job_parent << ' ' << cost_to_take[least_expensive_job_parent] << ' ' << x[least_expensive_job_parent] << endl;
pq.push(least_expensive_job_parent);
}
}
cout << x[0] - s << endl;
}
