'''
import os
os.chdir("C:\Users\jborthen\Desktop\Python\HackerRank")
execfile("finding-the-percentage.py")
'''

N = int(raw_input())
grades = {}
for i in range(0,N):
	input_string = str(raw_input())
	input_string = input_string.split(" ")
	grades[input_string[0]] = input_string[1:4]

student = str(raw_input())
average = (int(grades[student][0])+int(grades[student][1])+int(grades[student][2]))/3
print "{:.2f}".format(average)