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

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        WriteLine(XMX(n, m));
    }
    static long XMX(int n, int m)
    {
        if (n % 2 == 0)
        {
            return (long)n * m;
        }
        else if (n > 2)
        {
            var nf = (long)n / 2 * 2;
            var one = 0L;
            var ans = 0L;
            for (var b = 30; b >= 0; --b)
            {
                if (((m >> b) & 1) != 0)
                {
                    ++one;
                    ans += nf << b;
                }
                else
                {
                    ans += (Math.Min(n, one) / 2 * 2) << b;
                }
            }
            return ans;
        }
        else
        {
            return 0;
        }
    }
}