I drank 2/3 of 1/3 for the second time, that is, 2/3 * 1/3 = 2/9, leaving 2/3-2/9 = 4/9.

I drank 4/9+0/3 of 65438 for the third time, that is, 4/9 * 1/3 = 4/27, leaving 4/9-4/27 = 8/27.

Drink 8/27+0/3 of 65438 for the fourth time, which means 8/27 * 1/3 = 8/8 1.

I drank it four times1/3+2/9+4/27+8/81= 65/81.