def get_workflow_min_job_memory(complexity):
    """Return minimal job memory from workflow complexity.

    :param complexity: workflow complexity list which consists of number of initial jobs and the memory in bytes they require. (e.g. [(8, 1073741824), (5, 2147483648)])
    :return: minimal job memory (e.g. 1073741824)
    """
    if not complexity:
        return 0
    return min(complexity, key=lambda x: x[1])[1]