using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(FindNextSquare(155));

        Console.WriteLine(FindNextSquare(121));

        Console.WriteLine(FindNextSquare(625));

        Console.WriteLine(FindNextSquare(319225));

        Console.WriteLine(FindNextSquare(15241383936));

    }

    public static long FindNextSquare(long num)

    {

        if(System.Math.Sqrt(num) % 1 == 0)

            return (long)System.Math.Pow(System.Math.Sqrt(num) + 1, 2);

        else

            return -1;

    }

}