if __name__ == "__main__":

    n = int(input())
    student_marks: dict[str, list[float]] = {}

    for _ in range(n):
        name, *line = input().split()
        scores = list(map(float, line))
        student_marks[name] = scores

    query_name = input()

    average = sum(student_marks[query_name]) / len(student_marks[query_name])

    print(f"{average:.2f}")