FUNCTION ran1(idum)

INTEGER idum,IA,IM,IQ,IR,NTAB,NDIV

REAL ran1,AM,EPS,RNMX

PARAMETER (IA=16807,IM=2147483647,AM=1./IM,IQ=127773,IR=2836,

*NTAB=32,NDIV=1+(IM-1)/NTAB,EPS=1.2e-7,RNMX=1.-EPS)

INTEGER j,k,iv(NTAB),iy

SAVE iv,iy

DATA iv /NTAB*0/, iy /0/

if (idum.le.0.or.iy.eq.0) then

idum=max(-idum,1)

do 11 j=NTAB+8,1,-1

k=idum/IQ

idum=IA*(idum-k*IQ)-IR*k

if (idum.lt.0) idum=idum+IM

if (j.le.NTAB) iv(j)=idum

11 continue

iy=iv(1)

endif

k=idum/IQ

idum=IA*(idum-k*IQ)-IR*k

if (idum.lt.0) idum=idum+IM

j=1+iy/NDIV

iy=iv(j)

iv(j)=idum

ran1=min(AM*iy,RNMX)

return

END