#include<iostream>

#include<algorithm>

#include<sstream>

#include<string>

using namespace std;

typedef long long ll;

int T;

int main()

{

	cin >> T;

	while (T--)

	{

		ll n;

		ll half;

		ll sum;

		string num;

		string ans;

		cin >> n;

		ans.resize(n, ' ');//这个很重要，重新分配了答案字符串的大小，方便分配组

		cin >> num;

		sum = n * (n + 1) / 2;//宝石的总和

		if (sum & 1) { cout << -1 << endl; continue; }//如果是奇数就直接输出-1

		half = sum / 2;//宝石分一半

		for (int i = n; i >= 1; i--){//从后面开始分

			if (half <= n &&  ans[half - 1] == ' '){//half<=n意味着可以直接从中挑人分组了

				if (num[half - 1] == '1') {

					ans[half - 1] = '3';

				}

				else {

					ans[half - 1] = '1';

				}

				break;

			}

			half -= i;//表示已经分配掉这个人了

			if (num[i - 1] == '1') {

				ans[i - 1] = '3';

			}

			else{

				ans[i - 1] = '1';

			}

		}

		for (int i = n; i >=1; i--){

			if (ans[i - 1] == ' '){

				if (num[i - 1] == '1') {

					ans[i - 1] = '4';

				}

				else {

					ans[i - 1] = '2';

				}

			}

		}

		cout << ans << endl;

	}

	return 0;

}