The next day, take the remaining 1/2, that is, 1/4.

etc

The fifth day is (1/2) 5 = 1/32.

The sixth day is (1/2) 6 = 1/64.

The tenth day is (1/2)10 =11024.

(2) Remaining (1/2) n on the nth day

(3)( 1/2)^n<； 1/ 1000000

Solving n & gt20

After about 20 days.