we need max result and x1/(x2/x3/.../xn) = x1/x2 * (x3...xn).

so we could jump to the solution.

```
public class Solution {
public string OptimalDivision(int[] nums) {
if(nums.Length <3) return string.Join("/", nums);
var arr = new int[nums.Length-1];
for(var i=1;i<nums.Length;i++){
arr[i-1] = nums[i];
}
return string.Format("{0}/({1})",nums[0].ToString(),string.Join("/", arr));
}
}
```