if __name__ == '__main__':
    n = int(input())

    student_marks = {}
    for _ in range(n):
        name, *line = input().split()
        scores = list(map(float, line))
        student_marks[name] = scores
    query_name = input()
    if student_marks[query_name]:
        total=round(sum(student_marks[query_name])/len(student_marks[query_name]),2)
        print(f"{total:.2f}")