import sys
import re

lines = []
for line in sys.stdin:
    lines.append(line)
bin_str = r"[01]*"
assert len(lines) == 3
assert re.fullmatch(r"[1-9]\d*\n", lines[0])
N = int(lines[0])
assert 1 <= N <= 500
assert re.fullmatch(fr"{bin_str}\n", lines[1])
S = lines[1].strip()
assert len(S) == 2 * N
assert re.fullmatch(fr"{bin_str}\n", lines[2])
T = lines[2].strip()
assert len(T) == 2 * N

x = [2 * int(S[i]) + int(S[i + N]) for i in range(N)]
y = [2 * int(T[i]) + int(T[i + N]) for i in range(N)]
for i in range(N):
    if (x[i] == 0) ^ (y[i] == 0):
        print(-1)
        exit()
print(2 * N)
for i in range(N):
    m = (y[i] - x[i]) % 3
    if m == 0:
        print(i)
        print(i)
    elif m == 1:
        print(i)
        print(i + 1)
    else:
        print(i + 1)
        print(i)