You can use max_element() function to find the position of the max element.
int main()
{
int num, arr[10];
int x, y, a, b;
cin >> num;
for (int i = 0; i < num; i++)
{
cin >> arr[i];
}
cout << "Max element Index: " << max_element(arr, arr + num) - arr;
return 0;
}