Buying shares X39187

You have $c$ coins, and you must make $n$ stock transactions. Each transaction involves buying or selling a share. All shares are worth one coin each. You can only buy if you have a coin, and can only sell if you have a share.

Given $n$ and $c$, print all possible sequences of operations.

Input

Input consists of $n$ and $c$. Suppose $1 \le c \le n \le 16$.

Output

Print in alphabetical order all possible sequences of $n$ operations when we start with $c$ coins. Use ‘b’ to buy and ‘s’ to sell.