【链接】 我是链接,点我呀:)

【题意】

在这里输入题意

【题解】

把gcd(a[1..n])放在输入的n个数之间。

【代码】

/*

  	1.Shoud it use long long ?

  	2.Have you ever test several sample(at least therr) yourself?

  	3.Can you promise that the solution is right? At least,the main ideal

  	4.use the puts("") or putchar() or printf and such things?

  	5.init the used array or any value?

  	6.use error MAX_VALUE?

  	7.use scanf instead of cin/cout?

*/

#include <bits/stdc++.h>

using namespace std;

const int N = 1000;

int n;

int a[N+10];

int main(){

	#ifdef LOCAL_DEFINE

	    freopen("F:\\c++source\\rush_in.txt", "r", stdin);

	#endif

	ios::sync_with_stdio(0),cin.tie(0);

	cin >> n;

	for (int i = 1;i <= n;i++){

		cin >> a[i];

	}

	int x = a[1];

	for (int i = 2;i <= n;i++)

		x = __gcd(x,a[i]);

	if (x!=a[1]){

		cout << -1 << endl;

	}else{

		cout << 2*n << endl;

	 	for (int i = 1;i <= n;i++){

	 	 	cout << a[i] <<' '<<x<<' ';

	 	}

	}

	return 0;

}