Reduce string

Give a string s of length l, and a set S of n sample string(s). We do reduce the string s using the set S by this way: - Wherever Si appears as a consecutive substring of the string s, you can delete (or not) it. - After each deletion, you will get a new string s by joining the part to the left and to the right of the deleted substring. Request By that way, try to reduce the given string s to