https://www.acmicpc.net/problem/2675
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int T = sc.nextInt();
for (int i = 0; i < T; i++) {
int R = sc.nextInt();
String S = sc.next();
for (int j = 0; j < S.length(); j++) {
for (int k = 0; k < R; k++) {
System.out.print(S.charAt(j));
}
}
System.out.println();
}
}
}