def main():
    n = int(input())
    a = [1]

    for i in range(n):
        a.append(int(input()) - a[i] if i%2 == 0 else a[i] - int(input()))
    a0 = min([a[i] for i in range(n+1) if i % 4 == 0 or i%4 == 3])
    a1 = min([a[i] for i in range(n+1) if i % 4 == 1 or i%4 == 2])
    if a1 < 1:
        print(-1)
        [print(i) for i in a]
    else:
        if a0 + a1 >= 2:
            print(n+1)
            [print(a[i]+1-a0) if  i % 4 == 0 or i%4 == 3 else print(a[i] - 1 + a0) for i in range(len(a))]
        else:
            print(-1)


if __name__ == "__main__":
    import sys
    import os
    if len(sys.argv) > 1:
        if sys.argv[1] == "-d":
            filename = "input1.txt"
            fd = os.open(filename, os.O_RDONLY)
            os.dup2(fd, sys.stdin.fileno())
            main()
    else:
        main()