def get_first_index_of_array(array):
    """
    this function is very usefull for get first index of array
    """
    return array[0]


assert get_first_index_of_array([1, 2, 3, 4, 5]) == 1
assert get_first_index_of_array([1, 2, 3, 4, 5]) != 2
assert get_first_index_of_array([1, 2, 3, 4, 5]) != 3
assert get_first_index_of_array([1, 2, 3, 4, 5]) != 4
assert get_first_index_of_array([1, 2, 3, 4, 5]) != 4