import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
 
public class Main {
 
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		for(int j=0;j<n;j++) {
			String[] str = br.readLine().split(" ");
			int num = Integer.parseInt(str[0]);
			String[] arry = str[1].split("");
 
			for(int i=0;i<arry.length;i++) {
				for (int k = 0; k < num; k++) {
					System.out.print(arry[i]);
				}
			}
		}
	}
}
 

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