program main

 implicit none

 integer             :: n, m
 real*8, allocatable :: re(:), im(:), a(:) 
 real*8              :: v1 
 integer             :: v2

 integer             :: i,j

!1)
 open(10,file='input.dat')
 read(10,*) n
 allocate(re(n))
 allocate(im(n))
 do i=1,n
    read(10,*) re(i), im(i)
 enddo   
 close(10)

!2)
 v1=0.d0
 v2=0 
 do i=1,n
    if (re(i).eq.im(i)) then
       v1=v1+re(i)**2
    endif
    if (re(i).eq.0.or.im(i).eq.0) then
       v2=v2+1
    endif
 enddo    
 write(*,*) 'Value of v1', v1
 write(*,*) 'Value of v2', v2

!3)
 if (v2.gt.0.and.n.gt.v2) then
    m=n-v2
    allocate(a(m))
    do i=1,m
       a(i)=re(i)-v1
    enddo   
 elseif (v2.eq.0) then
    m=2*n
    allocate(a(m))
    do i=1,n
       j=2*i-1
       a(j)=re(i)
       a(j+1)=im(i)
    enddo   
 endif 

!4)
  if (allocated(a)) then
     open(10,file='a.dat')
     do i=1,m
        write(10,100) i, a(i)
     enddo   
     deallocate(a)
  else
    write(*,*) 'Output file can not be generated'
  endif   
100 format(I5,F10.5)


 deallocate(re)
 deallocate(im)

 stop

end program main