program golf
    implicit none
    integer k, a, b, i, flag
    read(*,*) k
    read(*,*) a, b
    flag=0

    if ( b-a+1 >= k ) then
        write(*,*) "OK"
    else
        do i = a, b
            if ( mod(i,k)==0 ) then
                flag=1
            end if
        end do
        if ( flag==1 ) then
            write(*,*) "OK"
        else
            write(*,*) "NG"
        end if
    end if
end program golf