public static string isBalanced(string s)
{
    var lastLength = -1;
    while(s.Length != lastLength){
        lastLength = s.Length;
        s = s.Replace("{}", "");
        s = s.Replace("[]", "");
        s = s.Replace("()", "");
    }
    return s.Length == 0 ? "YES" : "NO";
}