Count Strings

You are given a string $S$ of size $N$. The string will consist of lowercase English alphabets. Let another string $T$ is formed using the characters from string $S$. The string $T$ must contain all the characters of string $S$ at least once and no more than the number of times they occur in S. For example $S$ = $abaacc$, then string $T$ can be $abc, acb, aaaccb$ etc but not $aabccc, aacc$. How