import sys


def input(): return sys.stdin.readline().rstrip()


def main():
    int(input())
    *a, = map(int, input().split())

    while len(a) > 1:
        if a[-1] == 0:
            a.pop()
        elif len(a) >= 4:
            a[-3] += a[-1]
            a.pop()
        else:
            break

    print(len(a)-1)
    print(*a, sep=' ')


if __name__ == '__main__':
    main()