#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);
}
vi profit(n + 1, 0);
vi require(n + 1, -inf);
for(int i = n; i > 0; i--) {
ll v = topSort[i];
profit[v] = val[v];
if(val[v] < 0) require[v] = -val[v];
ll prof = profit[v], req = require[v];
for(auto x : g[v]) {
ll curProf = profit[x] + profit[v];
ll curReq = max(req, require[x]);
if(curProf < 0) continue;
if(curReq < req || (curReq == req && curProf > prof)) {
req = curReq;
prof = curProf;
}
}
profit[v] = prof;
require[v] = req;
}
ll cur = s;
priority_queue<pp> q; // required minimum, vertex
q.push({0, 0});
while(q.size()) {
ll r = -q.top().first, v = q.top().second;
q.pop();
if(cur < r) break;
cur += val[v];
for(auto x : g[v]) {
if(profit[x] < 0) continue;
q.push({-require[x], x});
}
}
ll ans = cur - s;
cout << ans << '\n';
return 0;
}
