#nullable enable

using System.Numerics;

void Run()
{
    var x = long.Parse(String());
    var n = long.Parse(String());

    var i = 0L;
    var fail = Math.Min(n, int.MaxValue);
    while (fail - i > 1)
    {
        var m = (fail + i) >> 1;
        var p = (m + 1) * m;
        if (p <= Math.Abs(x) * 2) i = m;
        else fail = m;
    }
    if (x > 0) x -= i * (i + 1) / 2;
    else x += i * (i + 1) / 2;
    if (i < n && x <= 0) x += ++i;
    var d = (n - i) / 2;
    x += d;
    i += d * 2;
    while (i < n)
    {
        ++i;
        if (x > 0) x -= i;
        else x += i;
    }
    Out(x);
}

#region
AtCoderIO _io_;
var _backend_ = new StandardIOBackend();
_io_ = new(){ Backend = _backend_ };
Run();
_backend_.Flush();

string String() => _io_.Next();
int Int() => int.Parse(String());
void Out(object? x, string? sep = null) => _io_.Out(x, sep);

class AtCoderIO
{
    public required StandardIOBackend Backend { get; init; }

    Memory<string> _input = Array.Empty<string>();
    int _iter = 0;
    public string Next()
    {
        while (_iter >= _input.Length) (_input, _iter) = (Backend.ReadLine().Split(' '), 0);
        return _input.Span[_iter++];
    }

    public void Out(object? x, string? separator = null)
    {
        if (x == null) return;
        separator ??= Environment.NewLine;
        if (x is System.Collections.IEnumerable a and not string)
        {
            var objects = a.Cast<object>();
            if (separator == Environment.NewLine && !objects.Any()) return;
            x = string.Join(separator, objects);
        }
        Backend.WriteLine(x);
    }
}

class StandardIOBackend
{
    readonly StreamReader _sr = new(Console.OpenStandardInput());
    readonly StreamWriter _sw = new(Console.OpenStandardOutput()) { AutoFlush = false };
    public string ReadLine() => _sr.ReadLine()!;
    public void WriteLine(object? value) => _sw.WriteLine(value);
    public void Flush() => _sw.Flush();
}
#endregion

static class Extensions
{
    public static T[] Repeat<T>(this int time, Func<T> F) => Enumerable.Range(0, time).Select(_ => F()).ToArray();
}