import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = 18446744073709551615
inf = 4294967295
md = 10**9+7
# md = 998244353

n = II()
s = [int(c) for c in SI()]
t = [int(c) for c in SI()]

ans = []
for i in range(n):
    if (s[i], s[i+n]) == (0, 0) and (t[i], t[i+n]) != (0, 0):
        print(-1)
        exit()
    if (s[i], s[i+n]) != (0, 0) and (t[i], t[i+n]) == (0, 0):
        print(-1)
        exit()

for i in range(n):
    if (s[i], s[i+n]) == (0, 1):
        if (t[i], t[i+n]) == (1, 0):
            ans.append(i)
            ans.append(i+1)
        if (t[i], t[i+n]) == (1, 1):
            ans.append(i+1)
            ans.append(i)
    if (s[i], s[i+n]) == (1, 0):
        if (t[i], t[i+n]) == (0, 1):
            ans.append(i+1)
            ans.append(i)
        if (t[i], t[i+n]) == (1, 1):
            ans.append(i)
            ans.append(i+1)
    if (s[i], s[i+n]) == (1, 1):
        if (t[i], t[i+n]) == (0, 1):
            ans.append(i)
            ans.append(i+1)
        if (t[i], t[i+n]) == (1, 0):
            ans.append(i+1)
            ans.append(i)

print(len(ans))
print(*ans, sep="\n")