text: 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()
      numbers = student_marks[query_name]
      average = sum(numbers)/len(numbers)
      print(f'{average:.2f}')
  