import java.util.*;
import java.lang.*;
import java.io.*;

class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner scan = new Scanner(System.in);
		long s = scan.nextLong();
		double k = Math.floor(Math.sqrt(2 * s + 1));
		int ans = (int) k;
		System.out.println (ans);
	}
}