static int Nesting(string s)
{
    if (string.IsNullOrEmpty(s))
    {
        return 1;
    }

    var stack = new Stack<char>();
    foreach (var v in s)
    {
        if (v == ')')
        {
            if (stack.Count == 0 || stack.Pop() != '(')
            {
                return 0;
            }
        }
        else
        {
            stack.Push(v);
        }
    }

    return stack.Count == 0 ? 1 : 0;
}