vector<int> reverseArray(int n, vector<int> &nums)
{
    // Write your code here.
    int start = 0;
    int end = n-1;

    while(start<end){
        int temp = nums[start];
        nums[start] = nums[end];
        nums[end] = temp;

        start++;
        end--;
    }

    return nums;

}

long long sumFirstN(long long n) {
    // Write your code here.
    if(n==0){
      return 0;  
    } 
    

    return n + sumFirstN(n-1);
}