123B codeforces.com

123B codeforces.com

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace toys
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                string s = Console.ReadLine();
                string[] values = s.Split(' ');
                long n = long.Parse(values[0]);
                long k = long.Parse(values[1]);
                long count = 0;


                ulong[] t = new ulong[n];
                for (long i = 0; i < n; i++)
                {
                    t[i] = (ulong)(n - i);
                }

                for (long i = 0; i < n; i++)
                {
                    for (long j = i + 1; j < n; j++)
                    {
                        if ((long)(t[i] + t[j]) == k)
                            count++;
                    }
                }


                Console.WriteLine("count =" + count);
                Console.ReadKey();
            }
            catch (Exception e)
            {
                Console.WriteLine("Ошибка: " + e);
            }
            Console.ReadKey();

        }
    }
}