#include <bits/stdc++.h>

int32_t main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int n;
    int64_t S;
    std::cin >> n >> S;
    std::vector<int> profit(n + 1), dep(n + 1);
    dep[0] = -1;
    for (int i = 1; i <= n; i++) {
        std::cin >> profit[i] >> dep[i];
    }
    n++;
    std::vector<std::vector<int>> gr(n);
    for (int i = 1; i < n; i++) {
        gr[dep[i]].push_back(i);
    }

    using Fuck = std::pair<std::pair<int64_t, int64_t>, std::vector<int>>;
    std::vector<Fuck> fuck(n, {{-1, -1}, {}});
    for (int i = n - 1; i > 0; i--) {
        std::set<std::pair<Fuck, int>> set;
        if (profit[i] >= 0) {
            fuck[i] = {{0, profit[i]}, gr[i]};
        } else {
            for (int v : gr[i]) {
                if (fuck[v].first.first != -1) {
                    set.insert({fuck[v], v});
                }
            }
            int64_t sum = profit[i], min = profit[i];
            while (sum < 0 && set.size()) {
                auto [p1, id] = set.extract(std::prev(set.end())).value();
                auto &[p, vc] = p1;
                auto &[a, b] = p;
                min = std::min(min, sum + a);
                sum += b;
                for (int v : vc) {
                    if (fuck[v].first.first != -1) {
                        set.insert({fuck[v], v});
                    }
                }
            }
            if (sum < 0) {
                continue;
            } else {
                std::vector<int> nxt;
                for (auto &[a, b] : set) {
                    nxt.push_back(b);
                }
                fuck[i] = {{min, sum}, nxt};
                // set.insert({fuck[i], i});
            }
        }
    }

    int64_t sum = S;
    {
        std::set<std::pair<Fuck, int>> set;
        for (int v : gr[0]) {
            if (fuck[v].first.first != -1) {
                set.insert({fuck[v], v});
            }
        }
        while (set.size()) {
            auto [p1, id] = set.extract(std::prev(set.end())).value();
            auto &[p, vc] = p1;
            auto &[a, b] = p;
            if (sum + a < 0) {
                break;
            }
            sum += b;
            for (int v : vc) {
                if (fuck[v].first.first != -1) {
                    set.insert({fuck[v], v});
                }
            }
        }
    }

    std::cout << sum - S << "\n";

    return 0;
}