// https://qoj.ac/contest/1522/problem/8056
// Travel 2
#include<bits/stdc++.h>

using i64 = long long;
const int N = 3000;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout << std::fixed << std::setprecision(10);
    
    int t;
    std::cin >> t;
    while (t--) {
        std::string a, b;
        std::cin >> a >> b;
        
        if (b.size() == 1 || a.size() == 1) {
            std::cout << (b == a ? 0 : -1) << "\n";
            continue;     
        }
        int len1 = a.length(), len2 = b.length();

        int cnt = 0;
        std::vector<std::pair<int, int>> ans;
        for (int i = 0; i < a.size(); i++) {
            if (a[i] == '0') {
                cnt++;
                ans.emplace_back(i, i + 1);
            }
        } 
        if (len1 < len2) {
            for (int i = 0; i < len2 - len1; i++) {
                ans.emplace_back(1, 2);
                ans.emplace_back(1, 2);
                ans.emplace_back(2, 3);
            }
        } else if (len1 > len2) {
            for (int i = 0; i < len1 - len2; i++) {
                ans.emplace_back(i + 1, i + 2);
            }
            ans.emplace_back(2, len1 - len2 + 1);
            ans.emplace_back(2, 3);
        }

        int len = len2;
        for (int i = 0; i < len; i++) {
            if (b[i] == '0') {
                ans.emplace_back(i, i + 1);
                ans.emplace_back(i + 1, i + 2);
            }
        }
        std::cout << ans.size() << "\n";
        for (auto [i, j] : ans) {
            std::cout << i << " " << j << "\n";
        }
    }
    return 0;
}