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 WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            int sum = 0;
            int a = Convert.ToInt16(textBox1.Text);
            int b = Convert.ToInt16(textBox2.Text);
            if (a<0)
            { a = 0; }
            if (b<0)
            { b = 0; }
            if (a > b)
            {
                int Aux;
                Aux = a;
                a = b;
                b = Aux;
            }
            textBox1.Text = Convert.ToString(a);
            textBox2.Text = Convert.ToString(b);
            while (a < b)
            {
                if (a % 5 == 0)
                {
                    sum = sum + a;
                }
                a++;
            }
            label1.Text = Convert.ToString(sum);
        }
    }
}