The Fallen Knight

**"The things I do for love" - Jaime Lannister** Ser Jaime Lannister was the best swordsman in the whole of Westeros. But after Locke cut off his right hand, he could no longer fight. He is now trying to learn addition of numbers. He only knows how to add $1$ to each number. He does it correctly except when the last digit is $9$, he changes it to $0$. Given a number $N$ , you have to add $1$ to