题解 | #计算题目难度#

def difficulty(grade_list):
    sum=0
    c=0
    for i in range(len(grade_list)):
        sum+=grade_list[i]
        if grade_list[i]==100:
            # 记录满分数
            c+=1
# 平均分
    avg=sum/len(grade_list)
# 难度
    dif=avg/c
    return dif


n=list(map(int,input().split()))
# 调用函数
diff=difficulty(n)
print('%.1f'%diff)