program golf
integer i,K,A,B
read(*,*) K
read(*,*) A, B
i=0
if(B-A>=K) then
	write(*,*) "ok"
else
	do i=0, B-A
	    if(((A+i)/K)*K=A+i) then
        	write(*,*) "OK"
        else
        	write(*,*) "NO"
        end if
    end do
end if