module module1
sub main()
    dim str as string
    str=console.readline()
    dim a as string()
    a = split(str)
    dim b as string
    if a(0) >= a(1) * 2 then
        b = a(0) - a(1) * 2
        console.writeline(b)
    else
        console.writeline(0)
    end if
End sub
end module