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);