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()

avg = 0.00
num = 0.00
for f in student_marks[query_name]:
    num = num + 1
    avg = avg +f

avg = avg / num

print("{:.2f}".format(avg))