/*
Description:
Task
You are given a sorted integer array arr. It contains several uniq integers(negative, positive, or zero).

Your task is to find the largest d such that a + b + c = d, where a, b, c, and d are distinct elements of arr. If no such an element d found, return null.

Still not understand the task? Look at the following example ;-)

Example
For arr = [2,3,5,7,12], the output should be 12.

12 = 2 + 3 + 7
For arr = [2,16,64,256,1024], the output should be null.

No such an element d found.

For arr = [-100,-1,0,7,101], the output should be 0.

0 = -100 + -1 + 101
Note
3 < arr.length <= 50

-1000 <= arr[i] <= 1000

Happy Coding ^_^
*/
function findD(arr){
  let a = []
   for (let i=0;i<arr.length-2;i++){
     for (let j=i+1;j<arr.length-1;j++){
         for (let z=j+1;z<arr.length;z++){
           if (arr.includes(arr[i]+arr[j]+arr[z])&&
           Math.abs(arr[i])!==Math.abs(arr[j])&&
           Math.abs(arr[i])!==Math.abs(arr[z])&&
           Math.abs(arr[j])!==Math.abs(arr[z])
           )  a.push(arr[i]+arr[j]+arr[z])
       }  
     }  
   } 
   return a.length?Math.max(...a):null
}
