subroutine splint(xa,ya,y2a,n,x,y)

C + + + argument definitions + + +
      real x, y, y2a, ya, xa
      integer n

C + + + local variables
      integer klo, khi, k
      real h, a, b

      dimension xa(n),ya(n),y2a(n)
      klo=1
      khi=n
c.... begin debug lines
c        do i=1,13
c           write (56,*)'n=',n,' xa(i)=', xa(i),' ya(i)=',ya(i),
c     &     ' y2a(i)=',y2a(i)
c        end do
c ......end debug lines          
1     IF (KHI-KLO.GT.1) THEN
        K=(KHI+KLO)/2
        IF(XA(K).GT.X)THEN
          KHI=K
        ELSE
          KLO=K
        ENDIF
      GOTO 1
      ENDIF
      H=XA(KHI)-XA(KLO)
      IF (H.EQ.0.) PAUSE 'Bad XA input.'
      A=(XA(KHI)-X)/H
      B=(X-XA(KLO))/H
      Y=A*YA(KLO)+B*YA(KHI)+
     *      ((A**3-A)*Y2A(KLO)+(B**3-B)*Y2A(KHI))*(H**2)/6.
c.... debug line
        write(56,*)x,y       
      RETURN
      END