procedure main(a)
   every n := !a do write(right(n,15)," -> ",midM(n))
end

procedure midM(n,m)
   /m := 3
   n := abs(n)
   return n ? if (*n >= m) then
                 if (((*n-m) % 2) = 0) then (move((*n - m)/2),move(m))
                 else "wrong number of digits"
              else "too short"
end