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() num=[] sum=0

for i,j in student_marks.items():
    if i==query_name:
        num=j
        count=len(j)
        for k in num:
            sum+=k
val=(sum/count)
print(f'{val:.2f}')