function input1(nsta,npt,ir,x,y,z,np,n,m,l)
c                                                                             
c***************************************************************************
c     (1) function :                                                       
c         a. read input data from input file                                
c         b. generate the offsets for whole section                   
c     (2) variables :                                                         
c         nsta : number of stations                                           
c         sta  : x-coord. of station                                          
c         npt  : number of input points of each station                       
c         ofy  : y-coord. of input point                                      
c         ofz  : z-coord. of input point                                      
c         ir   : relation between local node number and global node number    
c     (3) note :                                                              
c         a. the max. number of input stations : 21
c         b. the max. number of input points of each station : 8              
c         c. the number of input points of each station must be the same
c     (4) files:
c         sphere.dat: input file (offset of the grid points)
c         output.dat: output file of the potential at centroid of each element
c*****************************************************************************
c
      integer ir(n,m),npt(n)
      real*8 x(l),y(l),z(l)
      integer nsta,np
      real*8 sta(30),ofy(30,20),ofz(30,20)
c
      open(9,file='sphere.dat',access='sequential',status='unknown')
      open(11,file='output.dat',access='sequential',status='unknown')
      read(9,*) nsta           
      nsta1=nsta-1
      do 10 i=1,nsta                                                         
         write(*,*) 'i=',i
         read(9,*) sta(i),npt(i)                                              
         write(*,*) sta(i),npt(i)
         nt=npt(i)                                                        
         do 10 j=1,nt                                                 
         read(9,*)  ofy(i,j),ofz(i,j)                               
         write(*,*) ofy(i,j),ofz(i,j)
10    continue                                                     
      do 20 i=1,nsta
         nt=npt(i)-1
         do 30 j=1,nt
            k=npt(i)-j
            ofz(i,npt(i)+j)=ofz(i,k)
            ofy(i,npt(i)+j)=-ofy(i,k)
 30      continue
         npt(i)=npt(i)*2-1
 20   continue	
      np=0                                                                 
      do 70 i=1,nsta                                                        
         nn=npt(i)                                                    
         do 80 j=1,nn                                           
            np=np+1                                   
            x(np)=sta(i)                                                      
            y(np)=ofy(i,j)                                                    
            z(np)=ofz(i,j)                                                 
            ir(i,j)=np                                         
 80      continue                                                       
 70   continue           
      input1=1.0
      return                                                               
      end