#include <bits/stdc++.h>

using namespace std;

using ll = long long;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, k, c;
	cin >> n >> k >> c;
	vector<vector<int>> g(n + 1);
	vector<int> a(n + 1);
	for (int i = 1; i <= n; i++) {
		int p, x;
		cin >> p >> x;
		if (p != 0) {
			g[p].push_back(i);
		}
		a[i] = x;
	}
	vector<multiset<int>> ms(n + 1);
	vector<int> cz(n + 1, 0);
	auto dfs = [&](auto self, int u) -> void {
		for (int v : g[u]) {
			self(self, v);
			if (ms[u].size() < ms[v].size()) {
				ms[u].swap(ms[v]);
				swap(cz[u], cz[v]);
			}
			cz[u] += cz[v];
			for (int e : ms[v]) {
				ms[u].insert(e);
			}
			ms[v].clear();
			if (cz[u] >= k) {
				cz[u] = k;
				ms[u].clear();
			} else {
				while (cz[u] + (int)ms[u].size() > k) {
					ms[u].erase(prev(ms[u].end()));
				}
			}
		}
		int x = a[u];
		while (!ms[u].empty() && *ms[u].begin() == 0) {
			ms[u].erase(ms[u].begin());
			cz[u]++;
		}
		while (x > 0 && !ms[u].empty()) {
			int e = *ms[u].begin();
			ms[u].erase(ms[u].begin());
			if (x >= e) {
				x -= e;
				cz[u]++;
			} else {
				ms[u].insert(e - x);
				x = 0;
			}
		}
		if (x > 0 && cz[u] < k) {
			int num = min((ll)x / c, (ll)k - cz[u] - (int)ms[u].size());
			cz[u] += num;
			x -= num * c;
			if (x > 0 && cz[u] + (int)ms[u].size() < k) {
				ms[u].insert(c - x);
				x = 0;
			}
		}
		if (cz[u] >= k) {
			cz[u] = k;
			ms[u].clear();
		} else {
			while (cz[u] + (int)ms[u].size() > k) {
				ms[u].erase(prev(ms[u].end()));
			}
		}
	};
	dfs(dfs, 1);
	ll r = (ll)cz[1] * c;
	for (int e : ms[1]) {
		r += (c - e);
	}
	cout << r << '\n';
	return 0;
}