/**
 * @file qoj8058-1.cpp
 * @author n685
 * @brief
 * @date 2024-06-25
 *
 *
 */
#include <bits/stdc++.h>

#ifdef LOCAL
#include "dd/debug.h"
#else
#define dbg(...) 42
#define dbgR(...) 4242
#define dbgP(...) 420
#define dbgRP(...) 420420
void nline() {}
#endif

void solve() {
  std::string a, b;
  std::cin >> a >> b;
  dbg(a);

  if (a.size() == 1 || b.size() == 1) {
    if (a == b) {
      std::cout << "0\n";
    } else {
      std::cout << "-1\n";
    }
    return;
  }

  std::vector<std::pair<int, int>> ans;
  auto query = [&](int l, int r) -> void {
    ans.emplace_back(l, r);
    __int128_t val = 0, mul = 1;
    for (int i = r, j = 0; i >= l; --i, ++j, mul *= 3) {
      val += mul * (a[i] == '1');
    }
    std::string b2;
    while (val > 0) {
      b2 += '0' + val % 2;
      val /= 2;
    }
    std::reverse(b2.begin(), b2.end());
    if (b2.empty()) {
      b2 += '0';
    }
    a = a.substr(0, l) + b2 + a.substr(r + 1);
    dbg(l + 1, r + 1, a);
  };
  for (int i = 1; i < static_cast<int>(a.size()); ++i) {
    if (a[i] == '0') {
      query(i - 1, i);
    }
  }
  for (int i = static_cast<int>(a.size()) - 2; i >= 1; --i) {
    query(i - 1, i);
  }
  query(1, static_cast<int>(a.size()) - 1);
  for (int i = 0; i < static_cast<int>(b.size()) - 2; ++i) {
    query(i, i + 1);
    query(i, i + 1);
    query(i + 1, i + 2);
  }
  for (int i = static_cast<int>(b.size()) - 1; i >= 1; --i) {
    if (b[i] == '0') {
      query(i - 1, i);
      query(i, i + 1);
    }
  }
  std::cout << static_cast<int>(ans.size());
  for (auto [l, r] : ans) {
    std::cout << l + 1 << ' ' << r + 1 << '\n';
  }
  dbg(b);
}

auto main() -> int {
#ifndef LOCAL
  std::cin.tie(nullptr)->sync_with_stdio(false);
#endif

  int t;
  std::cin >> t;
  // std::scanf("%d", &t);
  while (t--) {
    solve();
    nline();
  }
}