#include <bits/stdc++.h>
int t, n, cnt[2][2], tem[2];
char a[4001], b[4001];
std::vector<int> ans;
void reverse(const int &x) {
  if (!x) return;
  std::reverse(a + 1, a + x + 1);
  ans.push_back(x);
}
int main() {
  scanf("%d", &t);
  for (int fd = 1; fd <= t; fd++) {
    scanf("%s%s", a + 1, b + 1);
    n = strlen(a + 1);
    ans.clear();
    int sum = 0;
    memset(cnt, 0, sizeof cnt);
    for (int i = 1; i <= n; i += 2) ++cnt[a[i] - '0'][a[i + 1] - '0'];
    for (int i = 1; i <= n; i += 2) --cnt[b[i + 1] - '0'][b[i] - '0'];
    if (cnt[0][0] || cnt[1][1]) {
      puts("-1");
      continue;
    }
    int magic = 0;
    if (cnt[1][0]) {
      bool cando = 0;
      for (int i = 1, ind = 0; i <= n; i += 2) {
        memset(cnt, 0, sizeof cnt);
        reverse(i + 1);
        for (int i = 1; i <= n; i += 2) ++cnt[a[i] - '0'][a[i + 1] - '0'];
        for (int i = 1; i <= n; i += 2) --cnt[b[i + 1] - '0'][b[i] - '0'];
        if (!cnt[1][0] && !cnt[0][1]) {
          cando = 1;
          break;
        } else
          reverse(i + 1), ans.clear();
      }
      if (!cando)
        for (int i = 1, ind = 0; i <= n; i += 2) {
          memset(cnt, 0, sizeof cnt);
          std::reverse(b + 1, b + i + 2);
          for (int i = 1; i <= n; i += 2) ++cnt[a[i] - '0'][a[i + 1] - '0'];
          for (int i = 1; i <= n; i += 2) --cnt[b[i + 1] - '0'][b[i] - '0'];
          if (!cnt[1][0] && !cnt[0][1]) {
            cando = 1;
            magic = i + 1;
            break;
          } else
            std::reverse(b + 1, b + i + 2);
        }
      if (!cando) {
        puts("-1");
        continue;
      }
    }
    for (int i = 1; i <= n; i += 2) {
      for (int j = i; j <= n; j += 2) {
        if (a[j] == b[n - i + 1] && a[j + 1] == b[n - i]) {
          reverse(j - 1);
          reverse(j + 1);
          break;
        }
      }
    }
    printf("%d\n", ans.size() + (magic != 0));
    for (int i = 0; i < ans.size(); i++) printf("%d ", ans[i]);
    if (magic) printf("%d ", magic);
    putchar('\n');
  }
}
