Subtract by multiple of 10. for example:

minimum value of mulitple of 10 by which number is subtracted to give minimum positive number.

1. for 9 = 1 * 10-9 = 1

2. for 18= 2* 10- 18 = 2

3. for 27 = 3* 10-27= 3

4. for 36 = 4* 10 -36 = 4