#nullable enable

var input = Console.ReadLine()!.Split(' ');
var n = long.Parse(input[0]);
var m = int.Parse(input[1]);

if (n == 1)
{
    Console.WriteLine("NaN");
    return;
}

int SolveN(long s)
{
    var i = 1;
    var l = s;
    while (true)
    {
        while (i < l)
        {
            m--;
            if (m == 0) return i;
            i++;
        }
        i++;
        l += s;
    }
}

int SolveF(decimal s)
{
    var i = 1;
    var l = s;
    while (true)
    {
        var k = (long)l;
        while (i < k)
        {
            m--;
            if (m == 0) return i;
            i++;
        }
        while (i < l) i++;
        l += s;
    }
}

int Solve()
{
    for (var i = 1L; i * i <= n; i++) if (i * i == n) return SolveN(i);
    decimal l = 0;
    decimal r = n;
    for (var i = 0; i < 160; i++)
    {
        var mid = (l + r) / 2;
        if (mid * mid < n) l = mid;
        else r = mid;
    }
    return SolveF(l);
}
Console.WriteLine(Solve());