A positive integer n is a semi-1 number if exactly half of the integers from 1 through n contain the digit 1. For example, 16 is semi-1, because exactly 8 of the integers between 1 and 16 contain the digit 1:

{1, 10, 11, 12, 13, 14, 15, 16}.

Find the largest semi-1 number you can find!