sgu-111-111. Very simple problem(java大数)

import java.util.Scanner;
import java.math.*;

public class Solution {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner cin=new Scanner(System.in);
BigInteger bb;
while(cin.hasNextBigInteger()){
bb=cin.nextBigInteger();
BigInteger L=BigInteger.valueOf(1);
BigInteger R=BigInteger.valueOf(10);
R=R.pow(500);
while(L.compareTo(R)<0){
//System.out.println("L "+L);
//System.out.println("R "+R);
BigInteger m=L.add(R.subtract(L).add(BigInteger.valueOf(1)).shiftRight(1));
//System.out.println("m "+m);
if(m.pow(2).compareTo(bb)<=0){
L=m;
}
else{
R=m.subtract(BigInteger.valueOf(1));
}
}
System.out.println(L);
}
}
}