#include <iostream>
#include <cstring>

using namespace std;
const int N = 100;

char A[N], B[N];
int n, m;
using Pair = pair<int, int>;
#include <vector>

vector<Pair> ans;

void add(int a, int b) {
    ans.push_back(make_pair(a, b));
}

void sol() {
    cin >> A + 1;
    cin >> B + 1;    
    n = strlen(A + 1);
    m = strlen(B + 1);
    ans.clear();
    if (n == 1) {
        if (m == 1) {
            cout << "0\n";
        } else {
            cout << "-1\n";
        }
        return;
    }
    if (m == 1) {
        cout << "-1" << '\n';
        return;
    }
    if (A[n] == '0') {
        int idx = n;
        while (idx > 1 && A[idx] == '0' && A[idx - 1] == '0') idx --;
        if (idx != n) { // ..100..0. -> ..10
            add(idx, n);
        }
        n = idx;
        add(n - 1, idx); // ....10 -> ....11
        A[n] = '1';
    }
    int cnt1 = 0;
    for (int i = n; i > 0; --i) {
        if (A[i] == '0') { // ...0111 -> ...111
            add(i, i + 1);
        } else if (A[i] == '1') {
            cnt1 ++;
        }
    }
    n = cnt1;
    for (int i = 1; i <= cnt1; ++i) {
        A[i] = '1';
    }
    A[n + 1] = 0;
    // cout << " --- " << cnt1 << '\n';
    for (int i = 1; i <= cnt1 - 2; ++i) { // 111 -> 11
        add(1, 2);
        add(2, 4);
    }
    n = 2;
    for (int i = 1; i <= n; ++i) { 
        A[i] = '1';
    }
    A[n + 1] = 0;
    for (int i = m; i > 2; --i) {
        add(1, 2);
        add(1, 3); // +0
        if (B[i] == '1') { // +1
            add(2, 3);
        }
    }
    if (B[2] == '0') {
        add(1, 2);
        add(2, 3);
    }
    cout << ans.size() << '\n';
    for (auto x : ans) {
        cout << x.first << ' ' << x.second << '\n';
    }

}

int main() {
    ios::sync_with_stdio(0);
    int T;
    cin >> T;
    while (T --) {
        sol();
    }
    return 0;
}