A concave subsequence is a subsequence where the first and last elements are greater than all other elements in between. For example, [100, 0, 25, 11, 200] is concave, while [100, 0, 110, 200] is not since the third element is greater than the first element.

Given an array that contains a permutation of n integers, arr[n], determine length of the longest concave subsequence.

A permutation is a sequence of integers from 1 to n that contains each number exactly once. For example [1, 3, 2] is a permutation while [1, 2, 1] and [1, 2, 4] are not.

A subsequence is derived from a sequence by deleting zero or more elements without changing the order of the remaining elements. For example [3, 4] is a subsequence of [5, 3, 2, 4], but [4, 3] is not.

Example
n=6
arr = [4, 2, 6, 5, 3, 1]

There are three longest subsequences: [4, 2, 6], [4, 2, 5], and [4, 2, 3].
Return 3, the length of these subsequences.

Function Description
Complete the function maxLength in the editor below.

maxLength has the following parameter:
int arr[n]: the array

returns
int: the length of the longest subsequence having the required property

constraints
1 <= n <= 10^5
1 <= arr[i] <= n
arr is a permutation of integers from 1 to n.

Sample Input 0
5 arr[ ] size n=5
3 arr[ ] = [3,1,5,2,4]
1
5
2
4
Sample Output 0
4
Explanation
The longest subsequence satisfying the requirement is [3, 1, 2, 4].

Sample Input 1
5 arr[] size n = 5
1 arr = [1, 2, 3, 4, 5]
2
3
4
5
Sample Output 1
2
Explanation
my subsequence of 2 elements satisfies the requirements.

I have written this code:

int findLen(vector<int> vec){
    int ans = 0;
    for(int i=0;i<vec.size(); i++){
        for(int j=i+1;j<vec.size();j++){
            int a = vec[i];	
            int b = vec[j];
            bool bln = true;
            int count = 2;
            for(int k=i+1;k<j;k++){
                if(vec[k]<a && vec[k]<b){
                Count++;
                }
            }
            if(bln){
            ans = max(ans, count);
            }
        }
    }
    return ans;
}

It passed 9/15 cases.