if __name__ == '__main__':
    n = int(input())
    student_marks = {}
    
    for _ in range(n):
        line = input().split()
        name, scores = line[0], list(map(float, line[1:]))
        student_marks[name] = scores
        
    query_name = input().strip()
    query_score = student_marks[query_name]
    average_score = sum(query_score) / len(query_score)
    
    print(f"{average_score:.2f}")