public static string balancedSums(List<int> arr)
{
    var len = arr.Count;
    var total = arr.Sum(x => (long)x);
    long leftSum = 0;
    long rightSum = total;

    for (int i = 0; i < len; ++i)
    {
        rightSum = rightSum - arr[i];
        var leftIndex = (i == 0) ? 0 : i - 1;

        if (i > 0)
        {
            leftSum = leftSum + arr[leftIndex];
        }

        if (leftSum == rightSum)
        {
            return "YES";
        }
    }

    return "NO";
}