Amusing Numbers

Consider the integers from 1 to N inclusive. Order them lexicographically (that is, as in a dictionary). For example, for N = 11 the order is:

1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9.

Let $Q_{N,K}$ denote the position (counting from 1) of the number K in this ordering. For example, $Q_{11,2} = 4$.

Given K and M, find the smallest N such that $Q_{N,K} = M$.

A single line with two integers K and M ($1 \le K, M \le 10^9$), separated by a space.

If an N with $Q_{N,K} = M$ exists, print the smallest such N. Otherwise, print 0.