from bisect import bisect_left


def binary_search(arr: list, item) -> int:
    """
    performs a simple binary search on a sorted list

    :param arr: list
    :param item:

    :return: int
    """

    i = bisect_left(arr, item)
    if i != len(arr) and arr[i] == item:
        return i
    else:
        return -1