var page = 1;
var result = 0;
for (int i = 0; i < n; i++)
{
    var index = 1;
    while (index <= arr[i])
    {
        if (page == index)
            result++;
        if (index % k == 0 && index != arr[i])
            page++;
        index++;
    }
    page++;
}
return result;