@n = gets.to_i

@data = Array.new(@n)
@result = Array.new(@n+1)

@n.times{|i| @data[i] = gets.to_i}

1.upto(20){|k|
    def calc(k)
        b = k
        return false if b<=0 
        @result[0] = k
        @n.times{|i|
            b = @result[i+1] = (@data[i]-b) if i%2==0
            b = @result[i+1] = (b-@data[i]) if i%2==1
            if (b<=0 || 10**18<b)
                return false
            end
        }
        return true
    end
    if !calc(k)
        @result[0]=nil
        next
    else
        break
    end
}
if !@result[0]
    puts "-1";exit
end

puts @n+1
@result.each{|e| puts e}

#0.upto(@n-1){|i|
#    p @result[i]+@result[i+1] == @data[i] if i%2==0
#    p @result[i]-@result[i+1] == @data[i] if i%2==1
#}