remove 2 and z in available characters for groups
remove 2 and z in available characters for groups

France-ioi/bebras-platform,France-ioi/bebras-platform,be-oi/beoi-contest-platform,be-oi/beoi-contest-platform,France-ioi/bebras-platform,be-oi/beoi-contest-platform,France-ioi/bebras-platform,France-ioi/bebras-platform,be-oi/beoi-contest-platform,France-ioi/bebras-platform,be-oi/beoi-contest-platform,be-oi/beoi-contest-platform