Please help me with the calculation by friends who know a little about birthdays. Thank you.

This is not a matter of fortune telling.

You can't use eight characters if you have mental arithmetic.

Really, take three copper coins, if you don't use coins instead.

Put your hands together and think about your business. Shake it a few times and it will be fine naturally. Copper coins have several heads. Record them six times at a time, and then record the shaking time together and tell me.