#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vi vector<ll>
#define vvi vector<vector<ll>>
#define vs vector<string>
#define vc vector<char>
#define vb vector<bool>
#define vp vector<pair<ll, ll>>
#define vpp vector<pair<ll, pair<ll, ll>>>
#define pp pair<ll, ll>
#define qi queue<ll>
#define qp queue<pp>
#define pqi priority_queue<ll>
#define pqp priority_queue<pp>
#define mi map<ll, ll>
#define mpi map<pp, ll>
#define mip map<ll, pp>
#define mp map<pp, pp>
#define mb map<ll, bool>
#define si set<ll>
#define sp set<pp>
#define sc set<char>
#define mod 1000000007
#define inf INT_MAX
ll top_sort(ll v, vvi& g, vb& visited, vi& topSort, ll ind) {
visited[v] = true;
for(auto x : g[v]) {
if(visited[x]) continue;
ind = top_sort(x, g, visited, topSort, ind);
}
topSort[ind] = v;
return ind - 1;
}
int main() {
ifstream in("input.txt");
ofstream out("output.txt");
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n, s;
cin >> n >> s;
vi val(n + 1, 0);
vvi g(n + 1);
for(int i = 1; i <= n; i++) {
cin >> val[i];
ll prev;
cin >> prev;
g[prev].push_back(i);
}
vi topSort(n + 1, -1);
vb visited(n + 1, false);
ll ind = n;
for(int i = 0; i <= n; i++) {
if(visited[i]) continue;
ind = top_sort(i, g, visited, topSort, ind);
}
vector<multiset<pp>*> profit(n + 1);
for(int i = n; i >= 0; i--) {
ll v = topSort[i];
ll req = max(0LL, -val[v]);
ll biggest = -1;
for(auto x : g[v]) {
if(biggest == -1 || profit[x]->size() > profit[biggest]->size()) {
biggest = x;
}
}
if(biggest == -1 || profit[biggest]->size() == 0) {
profit[v] = new multiset<pp>();
}
else {
profit[v] = profit[biggest];
}
auto& cur = *profit[v];
if(cur.size() == 0 && val[v] < 0) {
continue;
}
if(cur.size() == 0) {
cur.insert({req, val[v]});
continue;
}
ll prof = val[v];
for(auto x : g[v]) {
if(x == biggest) continue;
auto& temp = *profit[x];
for(auto&[r, p] : temp) {
if(p <= 0) continue;
cur.insert({r, p});
}
delete(profit[x]);
}
while(prof <= 0 && cur.size() > 0) {
auto[r, p] = *cur.begin();
cur.erase(cur.find({r, p}));
if(prof <= 0) {
req = max(req, r - prof);
prof += p;
}
}
if(prof > 0) {
while(cur.size() > 0 && (*cur.begin()).first <= req) {
prof += (*cur.begin()).second;
cur.erase(cur.begin());
}
cur.insert({req, prof});
}
}
auto& fin = *profit[0];
ll ans = s;
for(auto[r, p] : fin) {
if(ans < r) break;
ans += p;
}
cout << ans - s << '\n';
return 0;
}
/*
6 6
-5 0
-1 1
10 2
-1 1
3 4
5 1
3 5
-5 0
4 1
4 1
ans: 3
5 2
-3 0
-5 1
7 2
9 0
3 2
ans: 11
5 4
-3 0
-2 1
100 2
-4 0
5 4
ans: 6
7 1
-3 0
-2 1
0 2
1 3
2 1
4 4
3 0
ans: 5
9 3
-3 0
-1 1
5 2
-2 1
4 4
-8 1
10 6
1 0
-2 8
*/
