/* package whatever; // don't place package name! */

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

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		System.out.println(sqrt(25));
	}
	
	public static double sqrt(int number) {
	    double t;     
	    double squareRoot = number / 2;     
	    do {
	        t = squareRoot;
	        squareRoot = (t + (number / t)) / 2;
	    } while ((t - squareRoot) != 0);     
	    return squareRoot;
	}
}