n = int(input()) # first input
sum = 0
scores_needed = 0
student_marks = {}
for i in range(n):
    line = input().split() # second set of input
    name = line[0]
    scores = line[1:]
    student_marks[name] = scores
query_name = input() # third input
for i in student_marks:# this for loop is the part of the code causing issue(s)
    print(i)
    if query_name == i:
        scores_needed = student_marks.get(query_name)
for score in scores_needed:
    sum += float(score)
print("{:.2f}".format(float(sum / len(scores_needed))))