#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
void work()
{
    string A, B;
    cin >> A >> B;
    int lb = B.length();
    if(A.length() == 1 && B.length() == 1){
        if(A == B) cout << "0\n";
        else cout << "-1\n";
        return;
    }
    if(A.length() == 1 || B.length() == 1){
        cout << "-1\n";
        return;
    }
    vector<pair<int, int>> ans;
    for(int i = 0; i < A.size(); ++i){
        if(A[i] == '0') ans.emplace_back(i, i + 1), A[i] = '1';
    }
    while(A.length() < lb){
        ans.emplace_back(A.length() - 1, A.length());
        ans.emplace_back(A.length() - 1, A.length());
        A += '1';
        ans.emplace_back(A.length() - 1, A.length());
    }
    if (A.length() > lb) {
        cout << "-1\n";
        return;
    }
    for(int i = lb - 1; i >= 0; --i){
        if(B[i] == '0'){
            ans.emplace_back(i, i + 1);
            ans.emplace_back(i + 1, i + 2);
        }
    }
    cout << ans.size() << "\n";
    for(auto i : ans){
        cout << i.first << " " << i.second << "\n";
    }
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t;
    cin >> t;
    while(t--)
        work();
}