#include <iostream>
#include <algorithm>
using namespace std;

int gx, gy, n, f;
int X[50], Y[50], c[50];
int dp[201][201];	//dp[x][y]

int main() {
	int i, x, y;
	
	cin >> gx >> gy >> n >> f;
	for (i = 0; i < n; i++) cin >> X[i] >> Y[i] >> c[i];
	
	for (x = 0; x <= gx; x++) for (y = 0; y <= gy; y++) dp[x][y] = 11451419;
	
	//同じクリスタルは何回でも使える～とした場合。
	dp[0][0] = 0;
	for (x = 0; x <= gx; x++) {
		for (y = 0; y <= gy; y++) {
			for (i = 0; i < n; i++) {
				dp[x + X[i]][y + Y[i]] = min(dp[x + X[i]][y + Y[i]], dp[x][y] + c[i]);
			}
			dp[x + 1][y] = min(dp[x + 1][y], dp[x][y] + f);
			dp[x][y + 1] = min(dp[x][y + 1], dp[x][y] + f);
		}
	}
	
	cout << dp[gx][gy] << endl;
	return 0;
}