def get_key(my_dict, val):
    """
    This function finds the key of a value in a dictionary.
    :param my_dict: The dictionary object to look for key
    :param val: the value of the target key
    :return: the first target key corresponding to the given value
             or string saying "key doesn't exist"
    """
    for key, value in my_dict.items():
        if val == value:
            return key

    return "key doesn't exist"