import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int gx = sc.nextInt();
        int gy = sc.nextInt();
        int n = sc.nextInt();
        int f = sc.nextInt();
        int[][] costs = new int[gx + 1][gy + 1];
        for (int i = 0; i <= gx; i++) {
            for (int j = 0; j <= gy; j++) {
                costs[i][j] = (i + j) * f;
            }
        }
        for (int i = 0; i < n; i++) {
            int x = sc.nextInt();
            int y = sc.nextInt();
            int c = sc.nextInt();
            for (int j = gx; j - x >= 0; j--) {
                for (int k = gy; k - y >= 0; k--) {
                    costs[j][k] = Math.min(costs[j][k], costs[j - x][k - y] + c);
                }
            }
        }
        System.out.println(costs[gx][gy]);
    }
}