大数快速开方

大数快速开方！

import java.math.BigInteger;
import java.util.Scanner;



public class Main
{
	public static void main(String[] args)
 	{ 
        Scanner sc = new Scanner(system.in);
        BigInteger N = sc.nextBigInteger();
        System.out.println(sqrt(N));
 	}
	
	public static BigInteger sqrt(BigInteger input)
	{
	    BigInteger x0 = BigInteger.TEN.pow((int)Math.sqrt(input.toString().length()));
	    BigInteger x1 = BigInteger.valueOf(11);
        while(!x0.equals(x1) && !x0.equals(x1.add(BigInteger.ONE)))
        {
        	x0 = new BigInteger(x1.toString());
        	x1 = x1.add(input.divide(x1)).divide(new BigInteger("2"));
        }
        return x1;
	}
}