package string;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.StringTokenizer;

class Bj2675 {

public static void main(String[] args) throws IOException {

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

int T = Integer.parseInt(br.readLine());

for (int i = 0; i < T; i++) {

StringTokenizer st = new StringTokenizer(br.readLine());

int n = Integer.parseInt(st.nextToken());

String text = st.nextToken();

StringBuilder sb = new StringBuilder();

if (text != null) {

for (int j = 0; j < text.length(); j++) {

char ch = text.charAt(j);

for (int k = 0; k < n; k++) {

sb.append(ch);

}

}

System.out.println(sb.toString());

}

}

br.close();

}

}