// yukicoder: No.451 575
// 2019.7.29 bal4u

#include <stdio.h>

typedef long long ll;

#if 1
#define gc() getchar_unlocked()
#define pc(c) putchar_unlocked(c)
#else
#define gc() getchar()
#define pc(c) putchar(c)
#endif

ll in() {   // 非負整数の入力
	ll n = 0; int c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

void out(ll n) { // 正整数の表示（出力）
	int i;
	char b[50];

	i = 0; while (n) b[i++] = n % 10 + '0', n /= 10;
	while (i--) pc(b[i]);
	pc('\n');
}

void outs(char *s) { while (*s) pc(*s++); }

#define LIM 1000000000000000000LL
ll a[100005];
ll b[100005]; int N;

int main()
{
	int i;
	ll ma, mi12, mi34, sft;
	
	N = (int)in(); for (i = 1; i <= N; i++) b[i] = in();
	if (N == 1) {
		if (b[1] == 1) goto NO;
		else outs("2\n1\n"), out(b[1]-1);
		return 0;
	}
	a[0] = 1;
	a[1] = b[1] - a[0], ma = 0, mi12 = mi34 = LIM+1;
	for (i = 2; i <= N; i++) {
		if (i & 1) a[i] = b[i] - a[i-1];
		else       a[i] = a[i-1] - b[i];
		if ((i & 3) == 1 || (i & 3) == 2) {
			if (a[i] <= 0) goto NO;
			if (a[i] < mi12) mi12 = a[i];
		} else {
			if (a[i] < mi34) mi34 = a[i];
			if (a[i] > ma) ma = a[i];
		}
	}
	if (mi34 > 0) {
		out((ll)N+1);
		for (i = 0; i <= N; i++) out(a[i]);
	} else {
		sft = -mi34+1;
		if (sft > mi12-1 || ma+sft > LIM) goto NO;
		out((ll)N+1);
		for (i = 0; i <= N; i++) {
			if ((i & 3) == 1 || (i & 3) == 2) out(a[i]-sft);
			else out(a[i]+sft);
		}
	}
	return 0;
NO: outs("-1");
	return 0;
}