#35744: You Cannot Pass?!


108081a1@gm.chihlee.edu.tw (何姿儀)


while True:
    try:
        numbers = input().split() # 讀到EOF會error
    except:
        break
 
    n = int(numbers[0])
    
    total = 0 # 初始值
    for grade in numbers[1:]:
        total += int(grade)
    
    average = total / n
    
    if average > 59:
        print('no')
    else:
        print('yes')