using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        if (n < 3)
        {
            WriteLine(n);
            return;
        }
        var ok = 33400;
        var ng = 1;
        while (ok - ng > 1)
        {
            var mid = (ok + ng) / 2;
            if (mid * (mid + 1) / 2 >= n) ok = mid;
            else ng = mid;
        }
        WriteLine(ok);
    }
}