B

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)
#define pb     push_back

int main()
{
    _test
    {
        int n;
        string s;
        cin>>n>>s;

        int cnt = 0;

        for(int i=0, j=n-1; i<j; i++, j--)
            cnt += (s[i] != s[j]);

        string ans = "";
        while(ans.size() < n+1)       ans += '0';

        for(int i=cnt; i<=n; i++)
            ans[i] = '1';

        if(n%2 == 0)
        {
            for(int i=cnt+1; i<=n; i+=2)
                ans[i] = '0';
        }

        int maxFlips = (n/2 - cnt)*2 + cnt + (n%2);

        for(int i=maxFlips+1; i<=n; i++)
            ans[i] = '0';

        cout<<ans<<"\n";
    }
}