今日彼女ができました///

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

enum CutPosition
{
    /// <summary>
    /// 側面
    /// </summary>
    Side,

    /// <summary>
    /// 前面
    /// </summary>
    Front,
}

public class Hello{
    public static void Main(){
        List<Material> input = new List<Material>();

        decimal x = 0m;
        decimal y = 0m;
        decimal z = 0m;
        decimal n = 0m;

        // レシピ入力行数
        var line1 = System.Console.ReadLine().Trim();
        string[] s = line1.Split(' ');

        if (s.Length != 4) throw new System.Exception("入力値が不正です");

        if (decimal.TryParse(s[0], out x)) { }
        if (decimal.TryParse(s[1], out y)) { }
        if (decimal.TryParse(s[2], out z)) { }
        if (decimal.TryParse(s[3], out n)) { }

        for (int i = 0; i < n; i++)
        {
            var line2 = System.Console.ReadLine().Trim();
            string[] cutPosition = line2.Split(' ');

            if (cutPosition.Length != 2) throw new System.Exception("切る位置情報が不正です - 1");

            CutPosition position;
            if (cutPosition[0] == "0")
                position = CutPosition.Side;
            else if (cutPosition[0] == "1")
                position = CutPosition.Front;
            else
                throw new System.Exception("切る位置情報が不正です - 2");

            input.Add(new Material
            {
                Key = position,
                Value = decimal.Parse(cutPosition[1]),
            });
        }

        if (input.Count != 0)
        {
            // 側面と水平に切った回数
            int sideCount = input.Count(a => a.Key == CutPosition.Side);

            // 前面と水平に切った回数
            int frontCount = input.Count(a => a.Key == CutPosition.Front);

            // 降順に並べ替える
            var query = from d in input 
                        orderby d.Value descending
                        group d by d.Key;

            // 長さ
            decimal len = 0m;

            List<decimal> x_len = new List<decimal>();
            List<decimal> y_len = new List<decimal>();

            foreach (IGrouping<CutPosition, Material> data in query)
            {
                int count = 0;

                if (data.Key == CutPosition.Side)
                {
                    len = x;
                    count = sideCount;
                }
                else if (data.Key == CutPosition.Front)
                {
                    len = y;
                    count = frontCount;
                }

                foreach (Material r in data)
                {
                    len = len - r.Value;
                    count--;

                    if (data.Key == CutPosition.Side)
                        x_len.Add(len);
                    else if (data.Key == CutPosition.Front)
                        y_len.Add(len);

                    len = r.Value;

                    // 最後に端を追加
                    if (count == 0)
                        if (data.Key == CutPosition.Side)
                            x_len.Add(len);
                        else if (data.Key == CutPosition.Front)
                            y_len.Add(len);

                }
            }

            decimal resultX = x;
            decimal resultY = y;

            if (x_len.Count != 0)
                resultX = x_len.Min();

            if (y_len.Count != 0)
                resultY = y_len.Min();

            System.Console.WriteLine(resultX * resultY * z);

        }

        System.Console.ReadKey();
    }
}

class Material
{
    public CutPosition Key { get; set; }
    public decimal Value { get; set; }
}