*$debug*$declare	subroutine interpo(n,a,f1,x,y1,ierr,m,eps)	real	v1(20,20),b(20)	real	a(*),f1(*)	real	s,bv,vv1,el,ec	integer	m2,is,ib,im,il,ir,i,j,k	m2=2*m	is=1	ib=n1	continue		im=(is+ib)/2		s=sign(1.,a(n)-a(1))********		write(*,*) is,ib,im,a(im),x		if((x-a(im))*s.lt.0)then		   ib=im		else if((x-a(im))*s.gt.0)then		   is=im		else		   y1=f1(im)		   ierr=0		   return		end if	if(is.lt.ib-1) go to 1	il=is-m+1	ir=ib+m-1********	write(*,*) il,ir	if(il.lt.1) then	   il=1	else if (ir.gt.n) then	   il=n-m2+1	end if********	write(*,*) il,ir	do i=1,m2		b(i)=a(i+il-1)-x		v1(1,i)=f1(i+il-1)	enddo	do i=2,m2	    k=i-1	    do j=i,m2		if(abs(b(j)).lt.abs(b(k))) k=j	    enddo	    if(k.ne.i-1) then		bv=b(k)		b(k)=b(i-1)		b(i-1)=bv		vv1=v1(1,k)		v1(1,k)=v1(1,i-1)		v1(1,i-1)=vv1	    endif	enddo	ierr=-9999	el=1	do i=2,m2	    do j=2,i	      v1(j,i)=(v1(j-1,j-1)*b(i)-v1(j-1,i)*b(j-1))/(b(i)-b(j-1))	    enddo	    ec=abs(1.-v1(i-1,i-1)/v1(i,i))	    if(ec.le.eps) then		y1=v1(i,i)		ierr=i		return	    elseif(ec.gt.el)then	    	y1=v1(i-1,i-1)		ierr=1-i		return	    endif	    el=ec	enddo	if(ierr.ne.0) y1=v1(m2,m2)	return	end