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()

# initiate the accumulators to store total marks
# and average scores
total_marks = 0
avg_score = 0
# get each name in student marks
for name in student_marks:
    # when name is equal to query name
    if name == query_name:
        # add the scores in the list for query student
        for score in student_marks[name]:
            total_marks += score
        # find its average
        avg_score = total_marks/len(student_marks[name])

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