import javax.swing.JOptionPane;

public class SteviloDiagonal {
    public static void main(String[] args) {
        // preberemo podatke
        String vhod = JOptionPane.showInputDialog("Stevilo diagonal katerega veckotnika vas zanima?");
        int n = Integer.parseInt(vhod);

        // izracunamo stevilo diagonal
        int stDiagonal = n * (n - 3) / 2;

        // izpisemo rezultat
        System.out.println(n + "-kotnik ima " + stDiagonal + " diagonal.");
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace SteviloDiagonal {
class SteviloDiagonal {
    static void Main(string[] args) {
        //preberemo podatke
        Console.Write("Stevilo diagonal katerega veckotnika vas zanima? ");
        int n = Int32.Parse(Console.ReadLine());

        // izracunamo stevilo diagonal
        int stDiagonal = n * (n - 3) / 2;

        // izpisemo rezultat
        Console.WriteLine(n + "-kotnik ima " + stDiagonal + " diagonal.");
        Console.ReadKey();
    }
}
}

#!C:/Python30/python
#-*-encoding: utf-8 -*-
# -*- coding: latin-1 -*-

#preberemo podatke
n= int(input("Stevilo diagonal katerega veckotnika vas zanima?"))    
#izracunamo stevilo diagonal
stDiagonal = n * (n - 3) / 2;

#izpisemo rezultat
print (n,"-kotnik ima",stDiagonal,"diagonal.")