Is It String Matching

You have been given two strings $A$ and $B$ of length $N$ and $M$ consisting of lowercase alphabets respectively. A string is considered nice if its an anagram of string $B$. Recall that, a string $S$ is called an anagram of the string $T$, if it is possible to rearrange letters in $S$ so that it is identical to the string $T$. For example, the string "aab" is an anagram of the string "aba"