Нахождение среднего гармонического - C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace массив_целых_чисел
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void radioButton3_CheckedChanged(object sender, EventArgs e)
        {
 
        }
 
        private void radioButton4_CheckedChanged(object sender, EventArgs e)
        {
 
        }
 
        private void label4_Click(object sender, EventArgs e)
        {
 
        }
 
        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Clear();
            textBox2.Clear();
            textBox3.Clear();
            radioButton1.Checked = false;
            radioButton2.Checked = false;
            radioButton3.Checked = false;
            radioButton4.Checked = false;
            checkBox1.Checked = false;
            checkBox2.Checked = false;
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Enabled = true;
            textBox2.Enabled = true;
            textBox3.Enabled = true;
            {
                int n;
                Double a, g, sa = 0, sg = 0;
                n = Convert.ToInt32(textBox1.Text);
                int[] mas = new int[n];
                Random random = new Random();
                for (int i = 0; i < n; i++)
                {
                    if (radioButton1.Checked)
                    {
                        mas[i] = random.Next(5, 10);
                        textBox2.Text += mas[i].ToString() + "  ";
                        sa = sa + mas[i];
                        sg = sg + 1 / mas[i];
                    }
                    if (radioButton2.Checked)
                    {
                        mas[i] = random.Next(10, 15);
                        textBox2.Text += mas[i].ToString() + "  ";
                        sa = sa + mas[i];
                        sg = sg + 1 / mas[i];
                    }
                    if (radioButton3.Checked)
                    {
                        mas[i] = random.Next(15, 20);
                        textBox2.Text += mas[i].ToString() + "  ";
                        sa = sa + mas[i];
                        sg = sg + 1 / mas[i];
                    }
                    if (radioButton4.Checked)
                    {
                        mas[i] = random.Next(20, 25);
                        textBox2.Text += mas[i].ToString() + "  ";
                        sa = sa + mas[i];
                        sg = sg + 1 / mas[i];
                    }
                }
                    if (checkBox1.Checked)
                    {
                        a = sa / n;
                        textBox3.Text = a.ToString();
                    }

                    if ((checkBox2.Checked) && (sg > 0))
 
                    {
                        g = n/sg;
                        textBox3.Text = g.ToString();
                    }
                    
                        if ((checkBox2.Checked) && (sg != 0))
 
                    { textBox3.Text = "Деление на 0"; }
 
                }
 
            }
        
        private void textBox2_TextChanged(object sender, EventArgs e)
        {
 
        }
 
        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {
 
        }
    }
}