module bikkuri
	implicit none
    
    contains
    
    subroutine kaijou(n,seki)
    
    	integer i,n,seki
        
        seki=1
        
        do i=n,1,-1
        	seki=seki*i
        end do

	end subroutine kaijou

end module bikkuri

program example
	use bikkuri
	implicit none

	integer :: n, a, b, i,x,y,z,wa=0
    
    read(*,*) n,a,b
    
    1 do i=1,n,1
    
    	if(i==a .or. i==b) then
        	goto 1
        else
        	call kaijou(n,x)
            call kaijou(i,y)
            call kaijou(n-i,z)
            
            wa=wa+(x/(y*z))
        end if
   end do
    
	write(*,*) mod(wa,(10**9+7))

end program