#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>>;
    auto cmp = [&](auto a, auto b) {
        return a.first.first < b.first.first;
    };
    std::vector<std::set<Fuck>> data(n);
    auto merge = [&](auto &a, auto &b) {
        if (a.size() < b.size()) {
            a.swap(b);
        }
        a.merge(b);
        b.clear();
    };
    for (int i = n - 1; i > 0; i--) {
        auto &set = data[i];
        if (profit[i] >= 0) {
            data[i].insert({{0, profit[i]}, gr[i]});
        } else {
            for (int v : gr[i]) {
                merge(set, data[v]);
            }
            int64_t sum = profit[i], min = profit[i];
            while (sum < 0 && set.size()) {
                auto p1 = 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) {
                    merge(set, data[v]);
                }
            }
            if (sum < 0) {
                continue;
            } else {
                int id = data.size();
                data.push_back({{{min, sum}, {id}}});
                data[i].swap(data[id]);
            }
        }
    }

    int64_t sum = S;
    {
        std::set<Fuck> set;
        for (int v : gr[0]) {
            merge(set, data[v]);
        }
        while (set.size()) {
            auto p1 = 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) {
                merge(set, data[v]);
            }
        }
    }

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

    return 0;
}