from collections import deque

q = int(input())
while q:
	q -= 1
	k = int(input())
	s = list(input())
	
	n = len(s)
	
	if k >= n:
		ans = s[0] * n
		print(ans)
		continue
	
	s = deque(s)
	for i in range(k):
		s.appendleft(s[0])
		s.pop()
	
	print("".join(s))