#include <bits/stdc++.h>

using namespace std;

typedef pair <int, int> pii;

void solve() {
    string a, b;
    cin >> a >> b;
    int n = a.size(), m = b.size();
    if (n == 1 || m == 1) {
        if (n != m) cout << "-1\n";
        else cout << "0\n";
        return ;
    }
    vector <pii> ans1(0), ans2(0);
    while (n > 2) {
        if (a[1] & 1) {
            ans1.emplace_back(1, 2);
            ans1.emplace_back(2, 4);
        }else {
            ans1.emplace_back(2, 3);
        }
        for (int i = 1; i < n; i ++) a[i] = a[i + 1];
        n --;
    }
    if (a[1] & 1) {
        ans1.emplace_back(1, 2);
        ans1.emplace_back(2, 3);
    }
    while (m > 2) {
        if (b[1] & 1) {
            ans2.emplace_back(1, 2);
            b[1] --;
        }
        if (b[2] & 1) {
            if (m > 3) {
                if (b[3] & 1) {
                    ans2.emplace_back(3, 4);
                }
                ans2.emplace_back(1, 3);
                for (int i = 3; i < m; i ++) b[i] = b[i + 1];
                m --;
            }else {
                ans2.emplace_back(2, 3);
                ans2.emplace_back(1, 3);
                ans2.emplace_back(1, 2);
                b[1] = '1'; m = 2;
                break;
            }
        }else {
            ans2.emplace_back(1, 3);
            b[1] = 49;
            for (int i = 2; i < m; i ++) b[i] = b[i + 1];
            m --;
        }
    }
    if (b[1] & 1) ans2.emplace_back(1, 2);
    reverse(ans2.begin(), ans2.end());
    cout << ans1.size() + ans2.size() << '\n';
    for (auto [l, r] : ans1) cout << l << ' ' << r << '\n';
    for (auto [l, r] : ans2) cout << l << ' ' << r << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    
    int T; cin >> T;
    while (T --) solve();
    
    return 0;
}