#include <bits/stdc++.h>

using namespace std;

const int INF = 1e8;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int gx, gy, n, f;
	cin >> gx >> gy >> n >> f;
	vector<int> x(n), y(n), c(n);
	for (int i = 0; i < n; i++) cin >> x[i] >> y[i] >> c[i];
	vector< vector<int> > dp(gx + 1, vector<int>(gy + 1, INF));
	dp[0][0] = 0;
	for (int i = 0; i < n; i++) {
		for (int j = gx; j >= x[i]; j--) {
			for (int k = gy; k >= y[i]; k--) {
				dp[j][k] = min(dp[j][k], dp[j - x[i]][k - y[i]] + c[i]);
			}
		}
	}

	int ans = INF;
	for (int i = 0; i <= gx; i++) {
		for (int j = 0; j <= gy; j++) {
			ans = min(ans, (gx + gy - i - j) * f + dp[i][j]);
		}
	}
	cout << ans << endl;
	return 0;
}