#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
#define ll long long
#define sz(a) ((int) (a).size())
#define vi vector < int >
#define me(a, x) memset(a, x, sizeof(a))
#define ull unsigned long long
#define ld __float128
#define pb emplace_back
using namespace std;
const int N = 1e6 + 7, mod = 998244353;
int n;
struct node {
	ll lim, delta;
	int id;
	node(ll A = 0, ll B = 0, int ID = 0) {
		lim = A;
		delta = B;
		id = ID;
	}
} a[N];
priority_queue<node>pq;
bool operator < (node a, node b) {
	return a.lim > b.lim;
} 
ll s;
int fa[N];
int f[N];
inline int find(int x) {
	return f[x] == x ? x : f[x] = find(f[x]);
}
vi e[N];
int main() {
	ios :: sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	cin >> n >> s;
	L(i, 1, n) {
		cin >> a[i].delta >> fa[i];
		if(a[i].delta < 0)a[i].lim = -a[i].delta;
		a[i].id = i;
	}
	L(i, 1, n) {
		f[i] = i;
	}
	L(i, 1, n)
		if(a[i].delta > 0)
			pq.push(a[i]);
	while(!pq.empty()) {
		auto u = pq.top();
		pq.pop();
		int p = u.id;
		if(find(p) != p) continue;
		if(!fa[p]) continue;
		if(a[p].delta <= 0)continue;
		int F = find(fa[p]);
		if(a[F].delta <= 0 || -a[F].delta + a[p].lim <= a[F].lim) {
			// cout << p << " mergeto " << F << endl;
			a[F].lim = max(a[F].lim, -a[F].delta + a[p].lim);
			a[F].delta += a[p].delta;
		} else {
			continue;
		}
		f[p] = F;
		if(a[F].delta > 0) {
			pq.push(a[F]);
		}
	}
	L(i, 1, n) {
		if(find(i) == i) {
			e[find(fa[i])].pb(i);
			// cout << i << " : " << a[i].lim << ' ' << a[i].delta << endl;
		}
	}
	ll org = s;
	priority_queue<pair<ll,int>>q;
	q.push({0, 0});
	while(!q.empty()) {
		int u = q.top().second;
		q.pop();
		// cout << "use " << u << endl;
		if(a[u].lim > s) {
			break;
		}
		s += a[u].delta;
		for(auto&v : e[u]) {
			if(a[v].delta >= 0) {
				q.push({-a[v].lim, v});
			}
		}
	}
	cout << s - org << '\n';
	return 0;
} 
/*
6 1
3 0
-3 1
-5 0
2 1
6 3
-4 5
*/