Subroutine oad_s_LAGRAN(i,x,a,sp,lagranRet)
#include "CPP_OPTIONS.h"
        INTEGER i
        _RS x
        _RL a(4)
        _RL lagranRet
        INTEGER sp

C-      local variables:
        INTEGER k
        _RL numer,denom

        numer = 1. _d 0
        denom = 1. _d 0

#ifdef TARGET_NEC_SX
!CDIR UNROLL=8
#endif /* TARGET_NEC_SX */
        do k=1,sp
         if ( k .ne. i) then
          denom = denom*(a(i) - a(k))
          numer = numer*(x    - a(k))
         endif
        enddo

        lagranRet = numer/denom

       END