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

public class Main {
    static int[][][] dp;
    static int[] xs;
    static int[] ys;
    static int[] cs;
    static int f;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int gx = sc.nextInt();
        int gy = sc.nextInt();
        int n = sc.nextInt();
        f = sc.nextInt();
        xs = new int[n];
        ys = new int[n];
        cs = new int[n];
        for (int i = 0; i < n; i++) {
            xs[i] = sc.nextInt();
            ys[i] = sc.nextInt();
            cs[i] = sc.nextInt();
        }
        dp = new int[n][gx + 1][gy + 1];
        System.out.println(dfw(n - 1, gx, gy));
    }
    
    static int dfw(int idx, int x, int y) {
        if (x < 0 || y < 0) {
            return Integer.MAX_VALUE / 2;
        }
        if (idx < 0) {
            return (x + y) * f;
        }
        if (dp[idx][x][y] == 0) {
            dp[idx][x][y] = Math.min(dfw(idx - 1, x, y), dfw(idx - 1, x - xs[idx], y - ys[idx]) + cs[idx]);
        }
        return dp[idx][x][y];
    }
    
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}