C P500      SOURCE    CHAT      05/01/13    02:08:31     5004
      SUBROUTINE P500(D,U,G,R,N,DT)
      IMPLICIT INTEGER(I-N)
      IMPLICIT REAL*8 (A-H,O-Z)
      REAL*8 D(N),U(N),G(N),R(N)
      DO 1 I=1,N
      R(I)=U(I)-G(I)/D(I)*DT
 1    CONTINUE
      RETURN
      END