Number of times of unit 1: once every ten times, for example, "1,1,2 1".

Number of times of 1 in decimal digits: there will be ten times for every digit of 100, for example, "10 ~ 19" has 10 times.

The frequency of 1 in hundreds: every 1000 will be 100, for example, "100 ~ 199" will be 100.

Multiply of 1 in thousands: because the number is only 2000, it can be directly calculated as "1000 ~ 1999".

*** 1000 times

Unit frequency: 2000÷ 10=200

Digits: 2000 ÷ 100 = 20,20 * 10 = 200 (because every digit of100 has a digit of10, the same is true below).

Hundreds of times: 20001000 = 2,2 *100 = 200.

Thousands of times: 1000

So the total number of times is: 200+200+1000 =1600.

Think about it ... 2000 pages seems to be 4000 pages. ...

The algorithm remains the same, and the answer seems to be 2200.