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()
student_scores = student_marks.get(query_name)

print(format(sum(student_scores)/len(student_scores),".2f"))