n=gets.to_i
b=Array.new(n)
for i in 0...n
  b[i]=gets.to_i
end
a=Array.new(n+1)
a[0]=0
for i in 0...n
  if i%2==0
    a[i+1]=b[i]-a[i]
  else
    a[i+1]=a[i]-b[i]
  end
end
x=a[0]
y=a[1]
for i in 0..n
  if i%4==0||i%4==3
    x=[a[i],x].min
  else
    y=[a[i],y].max
  end
end
if 1-x>y-1
  puts -1
else
  puts n+1
  for i in 0..n
    puts a[i]+(if i%4==0||i%4==3 then 1-x else x-1 end)
  end
end