import java.util.Arrays;
import java.util.Scanner;

public class Main {
    static Scanner in = new Scanner(System.in);

    public static void main(String[] args) {
        int Gx = in.nextInt(), Gy = in.nextInt(), N = in.nextInt(), F = in.nextInt();
        int[] x = new int[N], y = new int[N], c = new int[N];
        for (int i = 0; i < N; i++) {
            x[i] = in.nextInt();
            y[i] = in.nextInt();
            c[i] = in.nextInt();
        }
        int[][] dp = new int[Gx + 1][Gy + 1];
        for (int i = 0; i < Gx + 1; i++) {
            Arrays.fill(dp[i], Integer.MAX_VALUE);
        }
        dp[0][0] = 0;
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < Gx + 1; j++) {
                for (int k = 0; k < Gy + 1; k++) {
                    if (j != 0) {
                        dp[j][k] = Math.min(dp[j][k], dp[j - 1][k] + F);
                    }
                    if (k != 0) {
                        dp[j][k] = Math.min(dp[j][k], dp[j][k - 1] + F);
                    }
                    if (j - x[i] >= 0 && k - y[i] >= 0) {
                        dp[j][k] = Math.min(dp[j][k], dp[j - x[i]][k - y[i]] + c[i]);
                    }
                }
            }
        }
        System.out.println(dp[Gx][Gy]);
    }
}