n = gets.to_i

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

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

b = 1
result[0] = 1
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)
        puts "-1";exit
    end
}

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