String Equivalency

Given 2 strings $s1$ ,$s2$ . A string $s2$ is said to be $k$ equivalent to string $s1$ if string $s2$ contains all the characters element wise $k$ times in the string $s1$ where $1 \leq k$. We define 2 operations to be possible as you can insert and delete some characters in the string $s2$ but you are not allowed to change string $s1$. Determine the minimum number of operations to make the st