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

namespace ConsoleApp191
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int a = 1;
            while ((1 + a) * a / 2 < n)
            {
                a += 1;
            }
            Console.WriteLine(a);
            Console.ReadLine();
        }
    }
}