import java.io.*;
import java.util.*;
import java.util.Map.*;


public class Main_yukicoder496 {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		int gx = sc.nextInt();
		int gy = sc.nextInt();
		int n = sc.nextInt();
		int f = sc.nextInt();

		int[] x = new int[n];
		int[] y = new int[n];
		int[] c = new int[n];
		for (int i = 0; i < n; i++) {
			x[i] = sc.nextInt();
			y[i] = sc.nextInt();
			c[i] = sc.nextInt();
		}

		Map<Integer, Integer> hm = new HashMap<>();
		hm.put(enc(x[0], y[0]), c[0]);
		for (int i = 1; i < n; i++) {
			List<Integer> tmp = new ArrayList<>(hm.keySet());
			for (int e : tmp) {
				int xx = e / 1000;
				int yy = e % 1000;
				int cc = hm.get(e);

				int nx = xx + x[i];
				int ny = yy + y[i];
				int nc = cc + c[i];

				if (nx > gx || ny > gy) {
					continue;
				}

				int key = enc(nx, ny);
				if (!hm.containsKey(key)) {
					hm.put(key, nc);
				} else {
					if (hm.get(key) > nc) {
						hm.put(key, nc);
					}
				}
			}
		}

		int min = (gx + gy) * f;
		for (Entry<Integer, Integer> e : hm.entrySet()) {
			int xx = e.getKey() / 1000;
			int yy = e.getKey() % 1000;
			int cc = e.getValue();

			min = Math.min(min, cc + (gx - xx + gy - yy) * f);
		}

		pr.println(min);
	}

	private static int enc(int x, int y) {
		return x * 1000 + y;
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pr = new Printer(System.out);

		solve();

		pr.close();
		sc.close();
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}