import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int gx = sc.nextInt();
        int gy = sc.nextInt();
        int n = sc.nextInt();
        int f = sc.nextInt();
        int[] xArr = new int[n];
        int[] yArr = new int[n];
        int[] cArr = new int[n];
        for (int i = 0; i < n; i++) {
            xArr[i] = sc.nextInt();
            yArr[i] = sc.nextInt();
            cArr[i] = sc.nextInt();
        }
        int[][] costs = new int[gx + 1][gy + 1];
        for (int[] arr : costs) {
            Arrays.fill(arr, Integer.MAX_VALUE);
        }
        PriorityQueue<Path> queue = new PriorityQueue<>();
        queue.add(new Path(0, 0, 0));
        while (queue.size() > 0) {
            Path p = queue.poll();
            if (costs[p.x][p.y] <= p.value) {
                continue;
            }
            costs[p.x][p.y] = p.value;
            if (p.x < gx) {
                queue.add(new Path(p.x + 1, p.y, p.value + f));
            }
            if (p.y < gy) {
                queue.add(new Path(p.x, p.y + 1, p.value + f));
            }
            for (int i = 0; i < n; i++) {
                if (p.x + xArr[i] <= gx && p.y + yArr[i] <= gy) {
                    queue.add(new Path(p.x + xArr[i], p.y + yArr[i], p.value + cArr[i]));
                }
            }
        }
        System.out.println(costs[gx][gy]);
    }
    
    static class Path implements Comparable<Path> {
        int x;
        int y;
        int value;
        
        public Path(int x, int y, int value) {
            this.x = x;
            this.y = y;
            this.value = value;
        }
        
        public int compareTo(Path another) {
            return value - another.value;
        }
    }
}