program ABC165A
    implicit none
    integer(8)::K,A,B,i,flg=0
    read*,K,A,B

    do i=A,B
        if(mod(i,K)==0)then
            flg=1
            exit
        end if
    end do

    if(flg==0)print'(A)',"NG"
    if(flg==1)print'(A)',"OK"
end program ABC165A