We added Rated/Unrated options

We developed a new system where one can choose Rated or Unrated participation in contests. We will introduce this system from ABC230 on 3rd Dec. When registering for a rated contest, you can decide whether you want to be Rated or Unrated in advance. You can choose an option before the contest starts or in the first five minutes of the contest. If you choose Rated, your rating will be updated whether or not you open problems or make submissions. In a rated contest, you can open problems only after you choose Rated or Unrated participation. If you don't choose an option and five minutes have passed after the contest starts, you are considered Unrated. Also, if your rating doesn't fall within the rated range of the contest, you are automatically regarded as Unrated. We recommend you choose an option in the following way: - Rated: We encourage you to choose this option in general. Even if it's the first time you take part in a contest, we recommend this. - Unrated: If you don't expect your typical performance for some reason but still want to see the problems and solve them, use this option. Before a contest starts, you can switch Rated/Unrated by first canceling your registration and then registering for the contest again. Note that, after the contest starts, you can't cancel your registration even if it's the first five minutes of the contest, and thus you cannot change the option. For GP30 scores in AGCs, we don't change the rule. You can earn points whether you are rated or not.