Retrieving specific value from an ArrayList in ASP.Net

I have an array {65, 62, 60, 56, 52, 50, 26, 25, 20, 06, 05, 02}.

I want to retrieve the value that is either EQUAL TO 23 OR NEAREST SMALLER than 23.

I am able to achieve nearest that is 25 but unable to get 20.

Appreciate all the help.

    protected void Button1_Click(object sender, EventArgs e)
    {
        int a = Convert.ToInt32(TextBox1.Text);
        int b = Convert.ToInt32(TextBox2.Text);
        int c = Convert.ToInt32(TextBox3.Text);
        int d = Convert.ToInt32(TextBox4.Text);
        int ab = 10 * a + b;
        int ac = 10 * a + c;
        int ad = 10 * a + d;
        int ba = 10 * b + a;
        int bc = 10 * b + c;
        int bd = 10 * b + d;
        int ca = 10 * c + a;
        int cb = 10 * c + b;
        int cd = 10 * c + d;
        int da = 10 * d + a;
        int db = 10 * d + b;
        int dc = 10 * d + c;
        List<int> arr = new List<int> {ab,ac,ad,ba,bc,bd,ca,cb,cd,da,db,dc};
        int target = 23;
        var nearestH = arr.OrderBy(x => Math.Abs(x - target)).First();
        Label1.Text = nearestH.ToString();
    }

Thanks