def isFibo(n):
    test_1 = 5 * (n**2) + 4
    test_2 = 5 * (n**2) - 4
    
    # If n is a fibonacci number then test_1 or test_2 must be a perfect square
    
    if int(math.sqrt(test_1)) ** 2 == test_1 or int(math.sqrt(test_2)) ** 2 == test_2:
        return 'IsFibo'
    else:
        return 'IsNotFibo'