using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.IO;

class Program
{
    static void Main()
    {
        new Magatro().Solve();
    }
}

public class Scanner
{
    private StreamReader Sr;

    private string[] S;
    private int Index;
    private const char Separator = ' ';

    public Scanner(Stream source)
    {
        Index = 0;
        S = new string[0];
        Sr = new StreamReader(source);
    }

    private string[] Line()
    {
        return Sr.ReadLine().Split(Separator);
    }

    public string Next()
    {
        string result;
        if (Index >= S.Length)
        {
            S = Line();
            Index = 0;
        }
        result = S[Index];
        Index++;
        return result;
    }
    public int NextInt()
    {
        return int.Parse(Next());
    }
    public double NextDouble()
    {
        return double.Parse(Next());
    }
    public long NextLong()
    {
        return long.Parse(Next());
    }
    public decimal NextDecimal()
    {
        return decimal.Parse(Next());
    }
    public string[] StringArray(int index = 0)
    {
        Next();
        Index = S.Length;
        return S.Skip(index).ToArray();
    }
    public int[] IntArray(int index = 0)
    {
        return StringArray(index).Select(int.Parse).ToArray();
    }
    public long[] LongArray(int index = 0)
    {
        return StringArray(index).Select(long.Parse).ToArray();
    }
    public bool EndOfStream
    {
        get { return Sr.EndOfStream; }
    }
}

public class Magatro
{
    private int Gx, Gy, N, F;
    private int[] x, y, c;

    private int[,] Cost;

    private void Scan()
    {
        var cin = new Scanner(Console.OpenStandardInput());
        Gx = cin.NextInt();
        Gy = cin.NextInt();
        N = cin.NextInt();
        F = cin.NextInt();
        x = new int[N];
        y = new int[N];
        c = new int[N];
        for (int i = 0; i < N; i++)
        {
            x[i] = cin.NextInt();
            y[i] = cin.NextInt();
            c[i] = cin.NextInt();
        }
    }



    public void Solve()
    {
        Scan();
        Cost = new int[Gx + 1, Gy + 1];
        for (int i = 0; i <= Gx; i++)
        {
            for (int j = 0; j <= Gy; j++)
            {
                Cost[i, j] = int.MaxValue;
            }
        }

        Cost[0, 0] = 0;
        for (int k = 0; k < N; k++)
        {
            for (int i = Gx; i >= 0; i--)
            {
                for (int j = Gy; j >= 0; j--)
                {
                    if (Cost[i, j] == int.MaxValue)
                    {
                        continue;
                    }
                    int nextX = i + x[k];
                    int nextY = j + y[k];
                    if (nextX > Gx || nextY > Gy)
                    {
                        continue;
                    }
                    Cost[nextX, nextY] = Math.Min(Cost[nextX, nextY], Cost[i, j] + c[k]);
                }
            }
        }

        int anser = int.MaxValue;

        for (int i = 0; i <= Gx; i++)
        {
            for (int j = 0; j <= Gy; j++)
            {
                if (Cost[i, j] == int.MaxValue)
                {
                    continue;
                }
                anser = Math.Min(anser, Walk(i, j) + Cost[i, j]);
            }
        }

        Console.WriteLine(anser);
    }

    private int Walk(int x, int y)
    {
        int dist = (Gx - x) + (Gy - y);
        return F * dist;
    }
}