using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();

    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var t = NN;
        var ans = new string[t];
        for (var u = 0; u < t; ++u)
        {
            var k = NN;
            var s = ReadLine();
            if (k < s.Length)
            {
                ans[u] = string.Concat(Enumerable.Repeat(s[0], k).Concat(s.Take(s.Length - k)));
            }
            else
            {
                ans[u] = string.Concat(Enumerable.Repeat(s[0], s.Length));
            }
        }
        WriteLine(string.Join("\n", ans));
    }
}