An integer is round if it is greater than $0$ and the sum of its digits in decimal representation is a multiple of $10$. Find an optimal procedure to compute the $N$−th smallest round integer.
E.g., if $N=2$ then the answer is $28$. As the first round integer is $19$ (note that $1+9=10$) and the second round integer is $28$ (since $2+8=10$).