#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];
multiset<pair<ll, ll>> st[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;
    for(int to:g[v]) {
        dfs(to);
        if((int)st[to].size() > (int)st[v].size()) {
            st[to].swap(st[v]);
        }
        for(auto i:st[to]) {
            st[v].insert(i);   
        }
    }
    ll val = x[v], mn = min(0ll, val);
    while(val < 0) {
        auto [r, y] = (*st[v].rbegin());
        st[v].erase(st[v].find(*st[v].rbegin()));
        mn = min(mn, val + r);
        val += y;
    }
    while(!st[v].empty() && (*st[v].rbegin()).first >= mn) {
        auto [r, y] = (*st[v].rbegin());
        st[v].erase(st[v].find(*st[v].rbegin()));
        val += y;
    }
    st[v].insert({mn, val});
}
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 en = s, mx = s;
    vector<pair<ll, ll>> vec;
    for(auto [y, x]:st[0]) {
        vec.push_back({y, x});
    }
    reverse(vec.begin(), vec.end());
    for(auto [y, x]:vec) {
        if(en + y < 0) {
            break;
        }
        en += x;
    }
    cout << en - s << '\n';
}
int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); 

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

    while(t--) 
        test();

    return 0;
}