d = gets.chomp.to_i
left = -1
right = 10 ** 18
min = 10 ** 18
while right - left > 1
    mid = (left+right)/2
    x = mid.dup
    if x < d
        ok = true
        dist = x
        #print "xは" + "#{x}" + " " + "dは" + "#{d}" + "\n"
        until mid == 0
            mid = mid / 2
            dist += mid
            if dist == d
                min = [min,x].min
                #ok = true
            elsif dist > d
                ok = false
                break
            end
            #p dist
        end
    elsif x == d
        min = [min,x].min
        ok = true
    else
        ok = false
    end
    if ok == false
        right = x
    else
        left = x
    end
    # puts "\\"
    # p min
    # p right
    # p left
    # p ok
    # print "xは" + "#{x}" + " " + "dは" + "#{d}" + "\n" 
    # puts "----"
end
puts min