Given an array, find maximum sum of smallest and second smallest elements chosen from all possible sub-arrays. More formally, if we write all (nC2) sub-arrays of array of size >=2 and find the sum of smallest and second smallest, then our answer will be maximum sum among them.
 

Example 1:

Input : arr[] = [4, 3, 1, 5, 6]
Output : 11
Subarrays with smallest and 
second smallest are,
[4, 3]        
smallest = 3    second smallest = 4
[4, 3, 1]    
smallest = 1    second smallest = 3
[4, 3, 1, 5]    
smallest = 1    second smallest = 3
[4, 3, 1, 5, 6]    
smallest = 1    second smallest = 3
[3, 1]         
smallest = 1    second smallest = 3
[3, 1, 5]     
smallest = 1    second smallest = 3
[3, 1, 5, 6]    
smallest = 1    second smallest = 3
[1, 5]        
smallest = 1    second smallest = 5
[1, 5, 6]    
smallest = 1    second smallest = 5
[5, 6]         
smallest = 5    second smallest = 6
Maximum sum among all 
above choices is, 5 + 6 = 11

Input : arr[] = {5, 4, 3, 1, 6} 
Output : 9

Your Task:  
You don't need to read input or print anything. Your task is to complete the function pairWithMaxSum() which takes the array Arr[] and its size N as inputs and returns the maximum sum of smallest and second smallest elements chosen from all possible subarrays.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
2 ≤ N ≤ 10⁵
1 ≤ A[i] ≤ 10¹⁸