Java实现****************************************************

import java.util.Scanner;

public class Main {

public static void main(String[] args) {

// TODO Auto-generated method stub

Scanner scanner=new Scanner(System.in);

int n=scanner.nextInt();

int i;

for(i=(int)Math.sqrt(n);;i++)

{

if(i*i>n) break;

}

System.out.println(i*i);

}

}