using System; using System.Collections.Generic; using static System.Console; namespace ConsoleApp { class Program { static void Main(string[] args) { int N = int.Parse(ReadLine()); //等差数列 //k(k+1)/2 = n //√k(k+1) = √2n //√k*k < √k(k+1) = √2n < √(K+1)(k+1) //k<√2n