_{This problem is a programming version of Problem 93 from projecteuler.net}

By using each of the digits from the set, , exactly once, and making use of the four arithmetic operations and brackets/parentheses, it is possible to form different positive integer targets.

For example,

Note that concatenations of the digits, like , are not allowed.

Using the set, , it is possible to obtain thirty-one different target numbers of which 36 is the maximum, and each of the numbers to can be obtained before encountering the first non-expressible number.

Given a set of distinct digits, , find the largest possible integer such that each integer from to is expressible using elements of and following the above rules. If is also not expressible, output instead.

**Input Format**

The first line contains .

The second line contains space separated integers, the elements of .

**Constraints**

**Output Format**

Output a single integer, the answer to the problem.

**Sample Input**

```
4
1 2 3 4
```

**Sample Output**

```
28
```

**Explanation**

Explained in the statement.