On the first day 12, 3456 turns off work.

On duty at 34 o'clock the next day, 1256 took turns to get off work.

On the third day, I was on duty at 56, 1234 took turns to rest.

……

Three days is a cycle.

A person can study for two days every three days, so four days divided by two days can complete two cycles (that is, at least six days).

There is no mathematical method. ...