The Game of Pebbles

There is a pile of N stones. Two players alternate turns, and on each turn, a player must take between one and M stones, inclusive. The player who cannot make a move loses the game.

If you are the first player and want to ensure a win, how many stones should you take on your first turn? If winning is not possible, return 0.

Input

The input consists of two integers, N and M, where 1 ≤ N, M ≤ 1000.

Output

Output the number of stones you should take to guarantee a win, or 0 if no winning strategy exists.

Examples