using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (x, n) = (c[0], c[1]);
        var ok = 0L;
        var ng = Math.Min(n, 1_500_000_000L) + 1;
        while (ng - ok > 1)
        {
            var mid = (ok + ng) / 2;
            if (mid * (mid + 1) / 2 > Math.Abs(x)) ng = mid;
            else ok = mid;
        }
        if (x <= 0) x += ok * (ok + 1) / 2;
        else x -= ok * (ok + 1) / 2;
        if (x <= 0) x -= (n - ok) / 2;
        else x += (n - ok) / 2;
        if ((n - ok) % 2 == 1)
        {
            if (x <= 0) x += n;
            else x -= n;
        }
        WriteLine(x);
    }
}