"""
name: Nicholas Tamassia

Honor Code and Acknowledgments:

        This work complies with the JMU Honor Code.

       Comments here on your code and submission.
"""


def circular_search(in_list: list[int], search_item: int) -> int:

    # * Nest the recursive function to hide the start-end indexing
    # * from end user, which could introduce bad input (e.g. start > end)
    # * It also means we don't have to keep passing in_list and search_term over and over again.
    def recurse(start: int, end: int) -> int:
        if end - start == 0:
            return -1
        if end - start == 1:
            return start if in_list[start] == search_item else -1

        mid: int = (start + end) // 2

        if in_list[start] <= in_list[mid - 1]:
            if in_list[start] <= search_item and search_item <= in_list[mid - 1]:
                return recurse(start, mid)
            else:
                return recurse(mid, end)
        else:
            if in_list[mid] <= search_item and search_item <= in_list[end - 1]:
                return recurse(mid, end)
            else:
                return recurse(start, mid)

    return recurse(0, len(in_list))
    

def main():
    # your code here

    in_list: list[int] = list(map(int, input().split()))
    search_item: int = int(input())

    index = circular_search(in_list, search_item)

    print(index)


if __name__ == "__main__":
    main()