import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int gx = sc.nextInt();
		final int gy = sc.nextInt();
		final int N = sc.nextInt();
		final int F = sc.nextInt();
		
		int[] xs = new int[N];
		int[] ys = new int[N];
		int[] cs = new int[N];
		for(int i = 0; i < N; i++){
			final int x = sc.nextInt();
			final int y = sc.nextInt();
			final int c = sc.nextInt();
			
			xs[i] = x;
			ys[i] = y;
			cs[i] = c;
		}
		
		long[][] DP = new long[gy + 1][gx + 1];
		for(int y = 0; y <= gy; y++){
			for(int x = 0; x <= gx; x++){
				DP[y][x] = (y + x) * F;
			}
		}
		
		for(int index = 0; index < N; index++){
			for(int y = gy; y >= 0; y--){
				final int ny = y - ys[index];
				if(ny < 0){ continue; }
				
				for(int x = gx; x >= 0; x--){
					final int nx = x - xs[index];
					if(nx < 0){ continue; }
					
					DP[y][x] = Math.min(DP[y][x], DP[ny][nx] + cs[index]);
				}
			}
		}
		
		
		/*
		for(int y = 0; y <= gy; y++){
			for(int x = 0; x <= gx; x++){
				System.out.print(DP[y][x] + " ");
			}
			System.out.println();
		}
		//*/
		
		System.out.println(DP[gy][gx]);
	}
}