text: from functools import reduce
  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()
      acc = reduce((lambda value,acc:value+acc), student_marks[query_name])
      percentage = acc/len(student_marks[query_name])
      print("{:.2f}".format(percentage))
      
  