#nullable enable

#region
var (_input, _iter) = (Array.Empty<string>(), 0);
T I<T>() where T : IParsable<T>
{
    while (_iter >= _input.Length) (_input, _iter) = (Console.ReadLine()!.Trim().Split(' '), 0);
    return T.Parse(_input[_iter++], null);
}
#endregion

var n = I<int>();
var b = I<int>();
var ans = "NaN";
if (b % 2 != 0)
{
    var y = (long)(n - 1) * (b + 1) / 2 % b;
    ans = y.ToString();
}
Console.WriteLine(ans);