Pasha and Good Ones

Pasha has a string $A$, of length $N$, and an integer $K$. Consider a string $B$ of length $M$. A character $c$ in string $B$ is said to be *good*, if the difference between the total occurrences of $c$ and the total remaining characters in $B$ (other than $c$), is equal to $K$. Formally, if $\texttt{freq(c, B)}$ denotes the frequency of character $c$ in string $B$ of length $M$, then, the fol