Problem: This is the easy version of the problem. The difference between the versions is the constraint on n and the required number of operations. You can make hacks only if all versions of the problem are solved.

There are two binary strings a and b of length n (a binary string is a string consisting of symbols 0 and 1). In an operation, you select a prefix of a, and simultaneously invert the bits in the prefix (0 changes to 1 and 1 changes to 0) and reverse the order of the bits in the prefix.

For example, if a=001011 and you select the prefix of length 3, it becomes 011011. Then if you select the entire string, it becomes 001001.

Your task is to transform the string a into b in at most 3n operations. It can be proved that it is always possible.

Input

The first line contains a single integer t (1≤ t≤ 1000) — the number of test cases. Next 3t lines contain descriptions of test cases.

The first line of each test case contains a single integer n (1≤ n≤ 1000) — the length of the binary strings.

The next two lines contain two binary strings a and b of length n.

It is guaranteed that the sum of n across all test cases does not exceed 1000.

Output

For each test case, output an integer k (0≤ k≤ 3n), followed by k integers p_1,…,p_k (1≤ p_i≤ n). Here k is the number of operations you use and p_i is the length of the prefix you flip in the i-th operation.

Example

Input


5
2
01
10
5
01011
11100
2
01
01
10
0110011011
1000110100
1
0
1


Output


3 1 2 1
6 5 2 5 3 1 2
0
9 4 1 2 10 4 1 2 1 5
1 1

Note

In the first test case, we have 01→ 11→ 00→ 10.

In the second test case, we have 01011→ 00101→ 11101→ 01000→ 10100→ 00100→ 11100.

In the third test case, the strings are already the same. Another solution is to flip the prefix of length 2, which will leave a unchanged.

Solution (in PYTHON3):

Solution:
 
# from math import factorial as fac
from collections import defaultdict
# from copy import deepcopy
import sys, math
f = None
try:
	f = open('q1.input', 'r')
except IOError:
	f = sys.stdin
if 'xrange' in dir(__builtins__):
	range = xrange
# print(f.readline())
# sys.setrecursionlimit(10**6)

	
def print_case_iterable(case_num, iterable):
	print("Case #{}: {}".format(case_num," ".join(map(str,iterable))))

def print_case_number(case_num, iterable):
	print("Case #{}: {}".format(case_num,iterable))

def print_iterable(A):
	print (' '.join(A))

def read_int():
	return int(f.readline().strip())
def read_int_array():
	return [int(x) for x in f.readline().strip().split(" ")]
def rns():
	a =  [x for x in f.readline().split(" ")]
	return int(a[0]), a[1].strip()
def read_string():
	return list(f.readline().strip())
def ri():
	return int(f.readline().strip())
def ria():
	return [int(x) for x in f.readline().strip().split(" ")]
def rns():
	a =  [x for x in f.readline().split(" ")]
	return int(a[0]), a[1].strip()
def rs():
	return list(f.readline().strip())
def bi(x):
	return bin(x)[2:]





from collections import deque
import math
NUMBER = 10**9 + 7
# NUMBER = 998244353
def factorial(n) : 
	M = NUMBER
	f = 1
  
	for i in range(1, n + 1):  
		f = (f * i) % M # Now f never can  
						# exceed 10^9+7  
	return f
def mult(a,b):
	return (a * b) % NUMBER

def minus(a , b):
	return (a - b) % NUMBER

def plus(a , b):
	return (a + b) % NUMBER

def egcd(a, b):
	if a == 0:
		return (b, 0, 1)
	else:
		g, y, x = egcd(b % a, a)
		return (g, x - (b // a) * y, y)

def modinv(a):
	m = NUMBER
	g, x, y = egcd(a, m)
	if g != 1:
		raise Exception('modular inverse does not exist')
	else:
		return x % m
def choose(n,k):
	if n < k:
		assert false
	return  mult(factorial(n), modinv(mult(factorial(k),factorial(n-k)))) % NUMBER
from collections import deque, defaultdict 
import heapq


from types import GeneratorType
def bootstrap(f, stack=[]):
	def wrappedfunc(*args, **kwargs):
		if stack:
			return f(*args, **kwargs)
		else:
			to = f(*args, **kwargs)
			while True:
				if type(to) is GeneratorType:
					stack.append(to)
					to = next(to)
				else:
					stack.pop()
					if not stack:
						break
					to = stack[-1].send(to)
			return to

	return wrappedfunc


def dfs(g, timeIn, timeOut,depths,parents): 
	# assign In-time to node u 
	cnt = 0
	# node, neig_i, parent, depth
	stack = [[1,0,0,0]]
	while stack:
		v,neig_i,parent,depth = stack[-1]
		parents[v] = parent
		depths[v] = depth
		# print (v)
		if neig_i == 0:
			timeIn[v] = cnt    
			cnt+=1
		while neig_i < len(g[v]):
			u = g[v][neig_i]
			if u == parent:
				neig_i+=1
				continue
			stack[-1][1] = neig_i + 1
			stack.append([u,0,v,depth+1])
			break
		if neig_i == len(g[v]):
			stack.pop()
			timeOut[v] = cnt
			cnt += 1
  
# def isAncestor(u: int, v: int, timeIn: list, timeOut: list) -> str: 
# 	return timeIn[u] <= timeIn[v] and timeOut[v] <= timeOut[u] 

cnt = 0
@bootstrap
def dfs(v,adj,timeIn, timeOut,depths,parents,parent=0,depth=0):
	global cnt
	parents[v] = parent
	depths[v] = depth
	timeIn[v] = cnt
	cnt+=1
	for u in adj[v]:
		if u == parent:
			continue
		yield dfs(u,adj,timeIn,timeOut,depths,parents,v,depth+1)
	timeOut[v] = cnt
	cnt+=1
	yield 

def gcd(a,b): 
	if a == 0: 
		return b 
	return gcd(b % a, a) 
  
# Function to return LCM of two numbers 
def lcm(a,b): 
	return (a*b) / gcd(a,b) 
def get_num_2_5(n):
	twos = 0
	fives = 0
	while n>0 and n%2 == 0:
		n//=2
		twos+=1
	while n>0 and n%5 == 0:
		n//=5
		fives+=1
	return (twos,fives)
def shift(a,i,num):
	for _ in range(num):
		a[i],a[i+1],a[i+2] = a[i+2],a[i],a[i+1]

def equal(x,y):
	return abs(x-y) <= 1e-9
# def leq(x,y):
# 	return x-y <= 1e-9
def getAngle(a, b, c):
	ang = math.degrees(math.atan2(c[1]-b[1], c[0]-b[0]) - math.atan2(a[1]-b[1], a[0]-b[0]))
	return ang + 360 if ang < 0 else ang
def getLength(a,b):
	return math.sqrt((a[0]-b[0])**2 + (a[1]-b[1])**2)


from heapq import heapify, heappush, heappop

def bfs(adj):
	s = set()
	d = defaultdict(set)
	# print('\n'.join(map(str,E.items())))
	q = deque([])
	s.add(0)
	d[0].add(0)
	q.append((0,0))
	while len(q) > 0:
		v,depth = q.popleft()
		for u in adj[v]:
			if u not in s:
				s.add(u)
				d[depth+1].add(u)
				q.append((u,depth+1))
		# print(q)
	return d


@bootstrap
def dfs(u,top, adj,vis):
	vis[u] = 1
	for v,d in adj[u]:
		if vis[v]==2 or d==0:
			continue
		if vis[v] == 1:
			yield "No"
		x = yield dfs(v,top,adj,vis)
		if x == "No":
			yield "No"
	vis[u] = 2
	top.append(u)
	yield

def solution(a,b,n):
	res = []
	fi = 0
	se = n-1
	bi = n
	cnt = 0
	curr = n-1
	last = 'r'
	while fi < se:
		bi-=1
		# print(f'curr={curr},last={last},cnt={cnt},bi={bi},fi={fi},se={se}')
		length = se-fi+1
		if (a[curr] ^ cnt) == b[bi]:
			# print('yo')
			if last == 'r':
				se-=1
				curr = se
			else:
				fi+=1
				curr = fi
			continue
		# print('yo')
		if last == 'r' and a[fi]^cnt == b[bi]:
			a[fi]^=1
			res.append(1)
		elif last == 'l' and a[se]^cnt == b[bi]:
			res.append(1)
			a[se]^=1
		res.append(length)
		cnt^=1
		if last == 'r':
			fi+=1
			curr = fi
			last = 'l'
		else:
			se-=1
			curr = se
			last = 'r'
	if a[fi]^cnt != b[0]:
		res.append(1)

	res = [len(res)] + res
	return ' '.join(map(str,res))



	
def main():
	T = 1
	T = ri()
	for i in range(T):
		n = ri()
		a = [int(x) for x in rs()]
		b = [int(x) for x in rs()]
		# s = rs()
		# n,m	= ria()
		# adj = [list() for _ in range(n)]
		# for _ in range(m):
		# 	d,a,b=ria();
		# 	a-=1; b-=1
		# 	adj[a].append((b,d))
		# 	if d == 0:
		# 		adj[b].append((a,d))

		x = solution(a,b,n)

		# continue
		if 'xrange' not in dir(__builtins__):
			print(x)
		else:
			print >>output,str(x)# "Case #"+str(i+1)+':',
	if 'xrange' in dir(__builtins__):
		print(output.getvalue())
		output.close()

if 'xrange' in dir(__builtins__):
	import cStringIO
	output = cStringIO.StringIO()
#example usage:
#    for l in res:
#       print >>output, str(len(l)) + ' ' +  ' '.join(l)

if __name__ == '__main__':
	main()