import sys
input=lambda:sys.stdin.readline().rstrip()
N=int(input())
S=input()
T=input()
ans=[]
for i in range(N):
	a=int(S[i]+S[i+N],2)
	b=int(T[i]+T[i+N],2)
	if a*b:
		if (b-a+3)%3==1:
			ans.append(i)
			ans.append(i+1)
		elif (b-a+3)%3==2:
			ans.append(i+N)
			ans.append((i+N+1)%(2*N))
	elif a+b:
		print(-1)
		sys.exit()
print(len(ans))
for i in ans:
	print(i)