#include <bits/stdc++.h>

using namespace std;

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	
    int tc;

    cin >> tc;

    while(tc--)
    {
        int n;
        string s;
        cin >> n;
        cin >> s;

        while(n > 0)
        {
            int cnt0 = 0;
            int cnt1 = 0;
            for(auto ch : s)
            {
                if(ch=='0') cnt0+=1;
                else cnt1+=1;
            }

            if(cnt0==0 || cnt1==0) break;
            s.pop_back();
            s = s[0] + s;
            n-=1;
        }
        cout << s << '\n';
    }
	return 0;
}