Peter's smokes

Peter has n cigarettes. He smokes them one by one keeping all the butts. Out of k > 1 butts he can roll a new cigarette.
How many cigarettes can Peter have?

Input is a sequence of lines. Each line contains two integer numbers giving the values of n and k.

For each line of input, output one integer number on a separate line giving the maximum number of cigarettes that Peter can have.

4 3
10 3
100 5

5
14
124