#include <bits/stdc++.h>
using namespace std;
int t, n, cur;
char a[200002], tem[200001], p[200001];
map <char, int> ds;
int main()
{
    cin >> t;
    while (t--)
    {
        ds.clear(), cur = 0;
        cin >> n;
        for (int i = 1; i <= n; i++)
        {
            cin >> a[i];
            tem[i] = a[i];
        }
        sort(a + 1, a + n + 1);
        for (int i = 1; i <= n; i++)
            if (a[i] != a[i + 1])
                p[++cur] = a[i];
        for (int i = 1; i <= cur; i++)
            ds[p[i]] = i;
        for (int i = 1; i <= n; i++)
            cout << p[cur - ds[tem[i]] + 1];
        puts("");
    }
    return 0;
}