!
! $Id: ran1.F 2197 2015-02-09 07:13:05Z fairhead $
!
      FUNCTION RAN1(IDUM)
      IMPLICIT NONE
      REAL RAN1
      REAL,SAVE :: R(97)
      REAL,PARAMETER :: RM1=3.8580247E-6,RM2=7.4373773E-6
      INTEGER,SAVE :: IFF=0
      integer,save :: ix1,ix2,ix3
      INTEGER,PARAMETER :: M1=259200,IA1=7141,IC1=54773
      INTEGER,PARAMETER :: M2=134456,IA2=8121,IC2=28411
      INTEGER,PARAMETER :: M3=243000,IA3=4561,IC3=51349
      INTEGER :: IDUM,J

      IF (IDUM.LT.0.OR.IFF.EQ.0) THEN
        IFF=1
        IX1=MOD(IC1-IDUM,M1)
        IX1=MOD(IA1*IX1+IC1,M1)
        IX2=MOD(IX1,M2)
        IX1=MOD(IA1*IX1+IC1,M1)
        IX3=MOD(IX1,M3)
        DO 11 J=1,97
          IX1=MOD(IA1*IX1+IC1,M1)
          IX2=MOD(IA2*IX2+IC2,M2)
          R(J)=(REAL(IX1)+REAL(IX2)*RM2)*RM1
11      CONTINUE
        IDUM=1
      ENDIF
      IX1=MOD(IA1*IX1+IC1,M1)
      IX2=MOD(IA2*IX2+IC2,M2)
      IX3=MOD(IA3*IX3+IC3,M3)
      J=1+(97*IX3)/M3
      IF(J.GT.97.OR.J.LT.1) stop 1
      RAN1=R(J)
      R(J)=(REAL(IX1)+REAL(IX2)*RM2)*RM1
      RETURN
      END