`What is the problem?

//C++

void findZigZagSequence(vector < int > a, int n){

    sort(a.begin(), a.end());

    int mid = (n + 1)/2;

    int st = mid - 1;

    int ed = n - 1;

    while(st <= ed){

        swap(a[st], a[ed]);

        st = st + 1;

        ed = ed - 1;

    }

    for(int i = 0; i < n; i++){

        if(i > 0) cout << " ";

        cout << a[i];

    }

    cout << endl;

} `

running failed: compiler Message Wrong Answer

Input (stdin)

1

7

1 2 3 4 5 6 7

Your Output (stdout)

1 2 3 7 6 5 4

Expected Output

1 2 3 7 6 5 4