<bot token> - bot token from @BotFather. See instructions;
<chat id> - chat id of community. Other chats will be restricted. Use curl -X GET https://api.telegram.org/bot<YOUR_API_TOKEN>/getUpdates after sending a message get chat id;
<folder with photos> - a tree of folders with photos. Bot will use it to get random photo;
CRON_SPEC - set a time for photo of the day in cron format;
CRON_JITTER_SEC - set a jitter for photo of the day in seconds. Bot will send a photo at random time between CRON_SPEC and CRON_SPEC + CRON_JITTER_SEC. Can be zero.