You are given a sequence of digits. You must insert either a '+' (addition) operator or a '*' (multiplication) operator between each pair of adjacent digits in such a way that minimizes the value of the resulting expression. The expression should be evaluated using the standard order of operations (multiplication has a higher precedence than addition).
You will be given a String sequence. Perform the procedure described above on the sequence and return the resulting expression. If there are several possible answers, return the one that comes first lexicographically. Note that '*' comes before '+' lexicographically.