import java.util.ArrayList;
import java.util.Scanner;

public class WarpCrystal {

	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();
		ArrayList<Integer> cx = new ArrayList<>();
		ArrayList<Integer> cy = new ArrayList<>();
		ArrayList<Integer> cc = new ArrayList<>();
		for(int i = 0;i < N;i++){
			int x = s.nextInt(),y = s.nextInt(),c = s.nextInt();
			if(c < (x+y)*F){
				cx.add(x);
				cy.add(y);
				cc.add(c);
			}
		}
		s.close();
		int[][] mas = new int[Gx+1][Gy+1];
		for(int i =0;i <= Gx;i++){
			for(int j = 0;j <= Gy;j++){
				mas[i][j] = (i + j) * F;
			}
		}
		for(int i = 0;i < cx.size();i++){
			for(int j = Gx;j >= 0;j--){
				for(int k = Gy;k >= 0;k--){
					if(j - cx.get(i) >= 0 && k -cy.get(i) >= 0){
						mas[j][k] = Math.min(mas[j][k], mas[j-cx.get(i)][k-cy.get(i)]+cc.get(i));
					}
				}
			}
		}
		System.out.println(mas[Gx][Gy]);
	} 
}