if __name__ == '__main__':
    n = int(input())
    student_marks = {}

    # Reading input and storing in dictionary
    for _ in range(n):
        name, *line = input().split()
        scores = list(map(float, line))
        student_marks[name] = scores

    # Query for the student's name
    query_name = input()
    scores = student_marks[query_name]

    # Calculate the average
    average = sum(scores) / len(scores)

    # Print the average rounded to 2 decimal places
    print(f'{average:.2f}')