program main

  implicit none

  integer  :: n, i, i2, i3, j, ii
  integer, allocatable :: a(:), b(:), c(:)  
  integer   :: sum_b, sum_c, tmp, tmp1
  integer, allocatable :: d(:), m(:,:)

! 1)
  do
    write(*,*) 'Insert n'
    read(*,*) n
    if (n.gt.10) exit
  enddo  
  allocate(a(n))
  open(10,file='a.dat')
  do i=1,n
     read(10,*) a(i)
  enddo
  close(10)

! 2)  
  i3=0
  i2=0
  do i=1,n
     if (mod(i,3).eq.0) i3=i3+1
     if (mod(i,2).eq.0) i2=i2+1
  enddo
  write(*,*) 'i3', i3
  write(*,*) 'i2', i2
  allocate(b(i3))
  allocate(c(i2))
  ii=0
  j=0
  do i=1,n
     if (mod(i,3).eq.0) then
        ii=ii+1
        b(ii)=a(i)
     endif
     if (mod(i,2).eq.0) then
        j=j+1
        c(j)=a(i)
     endif
  enddo
  sum_b=sum(b)
  sum_c=sum(c)
  write(*,*) 'sum_b', sum_b
  write(*,*) 'sum_c', sum_c
 

! 3)
  if (sum_b.gt.sum_c) then
     allocate(d(i3+i2))
     d(1)=b(1)
     do i=1,i2
        d(i+1)=c(i)
     enddo  
     do i=1,i3-1
        d(i2+1+i)=b(i+1)
     enddo  
  else
     allocate(m(n,n))
     do i=1,n
        m(i,i)=a(i)
     enddo  
     tmp=sum_b*sum_c
     tmp1=sum_c-sum_b
     do i=1,n
        do j=i+1,n
           m(i,j)=tmp
        enddo  
     enddo  
     do i=1,n
        do j=i+1,n
           m(j,i)=tmp1
        enddo  
     enddo
  endif

! 4)

  open(10,file='b.dat')
  open(11,file='c.dat')
  do i=1,i3
     write(10,100) i, b(i)
  enddo
  do i=1,i2
     write(11,100) i, c(i)
  enddo
  close(10)
  close(11)
  if (sum_b.gt.sum_c) then
     open(10,file='d.dat')
     do i=1,i3+i2
        write(10,100) i,d(i)
     enddo
  else  
     open(10,file='m.dat')
     do i=1,n
        do j=1,n
           write(10,101), i,j,m(i,j)
        enddo  
     enddo  
  endif
  close(10)  

100 format(I4,I4)
101 format(I4,I4,I6)

  deallocate(a)
  deallocate(b)
  deallocate(c)
  if (sum_b.gt.sum_c) then
     deallocate(d)
  else
     deallocate(m)
  endif  

 stop

 end program main