using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace zad
{
    public partial class Form1 : Form
    {
        interface I1
        {
            double dodaj(double a, double b);
        }

        public class K1 : K2, I1
        {
            public double dodaj(double a, double b) { return a + b; }
            public override double odejmij(double a, double b)
            {
                return a - b;
            }
        }

        public abstract class K2
        {
            public abstract double odejmij(double a, double b);
            public double pomnoz(double a, double b) { return a * b; }
        }

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            K1 k1 = new K1();
            textBox3.Text = k1.dodaj(Convert.ToDouble(textBox1.Text), Convert.ToDouble(textBox2.Text)).ToString();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            K1 k1 = new K1();
            textBox3.Text = k1.odejmij(Convert.ToDouble(textBox1.Text), Convert.ToDouble(textBox2.Text)).ToString();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            K1 k1 = new K1();
            textBox3.Text = k1.pomnoz(Convert.ToDouble(textBox1.Text), Convert.ToDouble(textBox2.Text)).ToString();
        }
    }
}