n = int(input())
s = list(map(int, input()))
t = list(map(int, input()))
ans = []
for i in range(n):
    if s[i] | s[i+n] != t[i] | t[i+n]:
        print(-1)
        exit()
    if (s[i], s[i+n]) == (t[i], t[i+n]):
        continue
    if (s[i] ^ s[i+n], s[i]) == (t[i], t[i+n]):
        ans.append(i)
        ans.append(i + 1)
    else:
        ans.append(i + n)
        ans.append((i + 1 + n) % (2 * n))
print(len(ans))
print(*ans, sep='\n')