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()
    s = 0 
    n = 0 
    for nums in student_marks[query_name]:
        s += nums
        n += 1
    print(f"{s/n:.2f}")