import java.util.Scanner;
public class WarpCristal {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int Gx = s.nextInt(),Gy = s.nextInt(),N = s.nextInt(),F = s.nextInt();
		int[][] cost = new int[Gx+1][Gy+1];
		int[][] d = new int[Gx+1][Gy+1];
		
		for(int i = 0;i < N;i++){
			d[s.nextInt()][s.nextInt()] = s.nextInt();
		}
		s.close();
		for(int i = 0;i <= Gx;i++){
			for(int j = 0;j <= Gy;j++){
				cost[i][j] = (i+j)*F;
				for(int x = 0;x <= i;x++){
					for(int y = 0;y <= j;y++){
						if(d[x][y] != 0 && cost[i][j] > cost[i-x][j-y] + d[x][y]){
							cost[i][j] = cost[i-x][j-y] + d[x][y];
						}
					}
				}
			}
		}
		System.out.println(cost[Gx][Gy]);
	}

}