#include <bits/stdc++.h>
    
using namespace std;
    
typedef long long ll;
const int  N = 3e5 + 12, MOD = (int)1e9 + 7;

#define int ll
int n, p[N], x[N];
ll s, d[N];
vector<int> g[N], rt, ord[N];

void prec(int v) {
    d[v] = x[v];
    for(int to:g[v]) {
        prec(to);
        if(d[to] < 0) continue;
        d[v] += d[to];
    }
}
deque<pair<ll, ll>> deq[N];
void dfs(int v) {
    if(d[v] < 0) return;
    deque<pair<ll ,ll>> f;
    for(int to:g[v]) {
        dfs(to);
        deque<pair<ll, ll>> nv;
        int l = 0, r = 0;
        while(l < (int)f.size() || r < (int)deq[to].size()) {
            if(l == (int)f.size() || (r != deq[to].size() && deq[to][r].second >= f[l].second)) {
                nv.push_back(deq[to][r]);
                r++;
            } else {
                nv.push_back(f[l]);
                l++;
            }
        }
        f = nv;
    }
    ll val = x[v], mn = min(0ll, val);
    while(val < 0) {
        mn = min(mn, val + f[0].second);
        val += f[0].first;
        f.pop_front();
    }
    f.push_front({val, mn});
    deq[v] = f;
}
void test() {
    cin >> n >> s;
    for(int i = 1; i <= n; i++) {
        cin >> x[i] >> p[i];
        g[p[i]].push_back(i);
    }
    prec(0);
    dfs(0);
    ll st = s, en = s, mx = s;
    for(auto [x, y]:deq[0]) {
        if(en + y < 0) {
            break;
        }
        en += x;
    }
    cout << en - st << '\n';
}
int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); 

    int t = 1; 
    // cin >> t;

    while(t--) 
        test();

    return 0;
}