public static string isFibo(long n)
    {
        long first = 0;
        long second = 1;
        
        for(long i = 0; i < n; i++)
        {   
            long temp = second;
            second += first;
            first = temp;
            
            if(second == n)
                return "IsFibo";
            if(second > n)
                return "IsNotFibo";
        }
       return "IsNotFibo";
    }