program main


  integer :: n,r,nfac,rfac,nrfac,ncr,fac 

  write(*,*)" enter n & r"
  read(*,*)n,r 


   ncr=fac(n)/fac(r)*fac(n-r)
write(*,*)ncr

end program main


function fac(n)

integer ::n,i,fac

fac=1

do i=1,n
fac=fac*i 
end do 

end function