Hello, I've been trying to solve this problem 1811E - Живая последовательность and i couldnt The problem states that we want to delete all numbers that contain 4 as a digit and then find what is the number is position k . i read the editorial and i have a question,if you didnt solve it and dont wana see solution, ignore this blog. . . . the solution says we want delete one digit the we have to convert number from base 10 to base 9 and then add every digit by one where this digit >= 4. why we add 1 for those digit and if i want delete like 2 digit (6, 7) then i have to convert number from base 10 to base 8 ? and increase every digit >= 6 or >= 7 by one ? i didnt understand i i tried to see some expalin on youtube but no one say why we add one.

thank you very much

This is the second time this happened to me during the contest. I thought the problem was from the country, so I turned on the VPN, but nothing happened. This made me delay sending B by about 5 minutes and sending C also by about 10 minutes. Please, if this was verified by the site organizers, then cancel it. If it was from my browser or something that came back to me, then I am sorry about this blog. Thank you.