#include <bits/stdc++.h>
using namespace std;

using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, K;
    ll C;
    cin >> N >> K >> C;

    vector<int> parent(N + 1);
    vector<ll> A(N + 1);

    for (int i = 1; i <= N; i++) {
        cin >> parent[i] >> A[i];
    }

    vector<vector<int>> children(N + 1);
    for (int i = 2; i <= N; i++) {
        children[parent[i]].push_back(i);
    }

    // Path sum számítás
    vector<ll> path_sum(N + 1, 0);

    function<void(int)> dfs = [&](int u) {
        for (int v : children[u]) {
            path_sum[v] = path_sum[u] + A[v];
            dfs(v);
        }
    };

    path_sum[1] = 0;
    dfs(1);

    // levelek gyűjtése
    priority_queue<ll> pq;

    for (int i = 2; i <= N; i++) {
        if (children[i].empty()) {
            pq.push(path_sum[i]);
        }
    }

    ll result = 0;

    for (int i = 0; i < K && !pq.empty(); i++) {
        ll val = pq.top();
        pq.pop();
        result += min(val, C);
    }

    cout << result << "\n";
}