#pragma GCC optimize(3)  //O2优化开启
#include<bits/stdc++.h>
using namespace std;
#define int long long
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> PII;
const int mod=998244353;
const int MX=0x3f3f3f3f3f3f3f3f; 
//inline int read()                     //快读
//{
//    int xr=0,F=1; char cr;
//    while(cr=getchar(),cr<'0'||cr>'9') if(cr=='-') F=-1;
//    while(cr>='0'&&cr<='9')
//        xr=(xr<<3)+(xr<<1)+(cr^48),cr=getchar();
//    return xr*F;
//}
//void write(int x)                     //快写
//{
//    if(x<0) putchar('-'),x=-x;
//    if(x>9) write(x/10); putchar(x%10+'0');
//}
// 比 unordered_map 更快的哈希表
// #include <ext/pb_ds/assoc_container.hpp>
// using namespace __gnu_pbds;
// const int RANDOM = chrono::high_resolution_clock::now().time_since_epoch().count();
// struct chash {
//     int operator()(int x) const { return x ^ RANDOM; }
// };
// typedef gp_hash_table<int, int, chash> hash_t;

template<int P>
struct MInt {
    int x;
    constexpr MInt() : x{} {}
    constexpr MInt(ll x) : x{norm(x % getMod())} {}

    static int Mod;
    constexpr static int getMod() {
        if (P > 0) {
            return P;
        } else {
            return Mod;
        }
    }
    constexpr static void setMod(int Mod_) {
        Mod = Mod_;
    }
    constexpr int norm(int x) const {
        if (x < 0) {
            x += getMod();
        }
        if (x >= getMod()) {
            x -= getMod();
        }
        return x;
    }
    constexpr int val() const {
        return x;
    }
    explicit constexpr operator int() const {
        return x;
    }
    constexpr MInt operator-() const {
        MInt res;
        res.x = norm(getMod() - x);
        return res;
    }
    constexpr MInt inv() const {
        assert(x != 0);
        return power(*this, getMod() - 2);
    }
    constexpr MInt &operator*=(MInt rhs) & {
        x = 1LL * x * rhs.x % getMod();
        return *this;
    }
    constexpr MInt &operator+=(MInt rhs) & {
        x = norm(x + rhs.x);
        return *this;
    }
    constexpr MInt &operator-=(MInt rhs) & {
        x = norm(x - rhs.x);
        return *this;
    }
    constexpr MInt &operator/=(MInt rhs) & {
        return *this *= rhs.inv();
    }
    friend constexpr MInt power(MInt a, ll b) {
        MInt res = 1;
        for (; b; b /= 2, a *= a) {
            if (b % 2) {
                res *= a;
            }
        }
        return res;
    }
    friend constexpr MInt operator*(MInt lhs, MInt rhs) {
        MInt res = lhs;
        res *= rhs;
        return res;
    }
    friend constexpr MInt operator+(MInt lhs, MInt rhs) {
        MInt res = lhs;
        res += rhs;
        return res;
    }
    friend constexpr MInt operator-(MInt lhs, MInt rhs) {
        MInt res = lhs;
        res -= rhs;
        return res;
    }
    friend constexpr MInt operator/(MInt lhs, MInt rhs) {
        MInt res = lhs;
        res /= rhs;
        return res;
    }
    friend constexpr std::istream &operator>>(std::istream &is, MInt &a) {
        ll v;
        is >> v;
        a = MInt(v);
        return is;
    }
    friend constexpr std::ostream &operator<<(std::ostream &os, const MInt &a) {
        return os << a.val();
    }
    friend constexpr bool operator==(MInt lhs, MInt rhs) {
        return lhs.val() == rhs.val();
    }
    friend constexpr bool operator!=(MInt lhs, MInt rhs) {
        return lhs.val() != rhs.val();
    }
};

template<int V, int P>
constexpr MInt<P> CInv = MInt<P>(V).inv();

constexpr int P = 998244353;            //这里为自动模数
using mint = MInt<P>;           //mint是其定理的类型

string s,ss;

void icealsoheat(){
    
    cin>>s>>ss;

    if(s=="1"||ss=="1"){

        if(s==ss)cout<<"0\n";
        else{
            cout<<"-1\n";
        }
        return;

    }

    if(s=="0"||ss=="0"){
        if(s==ss)cout<<"0\n";
        else cout<<"-1\n";
        return ;
    }

    s=" "+s;
    ss=" "+ss;
    string now="";
    int le=0;
    vector<PII>ans;
    int sum=0;
    for(int i=1;i<s.size();i++){

        if(s[i]=='0'&&le==0){
            le=i;
        }
        else if(s[i]=='1'){
            if(le!=0){
                ans.push_back({le-sum,i-sum});
                sum+=i-le;
            }
            le=0;
            now+='1';
        }
    }

    if(le!=0){

        ans.push_back({le-sum,s.size()-1-sum});

        now+='0';   
        le=1;
    }

    int sz=now.size();
    now=" "+now;
    cout<<now<<"\n";

    for(int i=sz;i>1;i--){
        if(now[i]=='1'&&now[i-1]=='1'){
            ans.push_back({i-1,i});
            // cout<<i<<" "<<i-1<<"++\n";
            le+=2;
        }
    }

    ans.push_back({2,2+le-1});

    ans.push_back({1,2});

    ans.push_back({1,2});

    // int id=3;

    for(int i=ss.size()-1;i>=2;i--){

        if(i==2){

            if(ss[i]=='1'){
                ans.push_back({2,3});
                ans.push_back({1,2});
            }
            else{
                ans.push_back({2,3});
            }

        }
        else if(ss[i]=='1'){

            ans.push_back({1,2});
            ans.push_back({2,3});
            ans.push_back({1,2});

        }
        else{
            ans.push_back({1,2});
            ans.push_back({1,2});
        }

    }

    cout<<ans.size()<<"\n";

    for(auto [i,j]:ans){
        cout<<i<<" "<<j<<"\n";
    }

}
signed main(){
    ios::sync_with_stdio(false);          //int128不能用快读！！！！！！
    cin.tie();
    cout.tie();
    int _yq;
    _yq=1;
    cin>>_yq;
    while(_yq--){
        icealsoheat();
    }
}
//
//⠀⠀⠀             ⠀⢸⣿⣿⣿⠀⣼⣿⣿⣦⡀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠀⠀⠀ ⠀⢸⣿⣿⡟⢰⣿⣿⣿⠟⠁
//⠀⠀⠀⠀⠀⠀⠀⢰⣿⠿⢿⣦⣀⠀⠘⠛⠛⠃⠸⠿⠟⣫⣴⣶⣾⡆
//⠀⠀⠀⠀⠀⠀⠀⠸⣿⡀⠀⠉⢿⣦⡀⠀⠀⠀⠀⠀⠀ ⠛⠿⠿⣿⠃
//⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣦⠀⠀⠹⣿⣶⡾⠛⠛⢷⣦⣄⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣧⠀⠀⠈⠉⣀⡀⠀ ⠀⠙⢿⡇
//⠀⠀⠀⠀⠀⠀⢀⣠⣴⡿⠟⠋⠀⠀⢠⣾⠟⠃⠀⠀⠀⢸⣿⡆
//⠀⠀⠀⢀⣠⣶⡿⠛⠉⠀⠀⠀⠀⠀⣾⡇⠀⠀⠀⠀⠀⢸⣿⠇
//⢀⣠⣾⠿⠛⠁⠀⠀⠀⠀⠀⠀⠀⢀⣼⣧⣀⠀⠀⠀⢀⣼⠇
//⠈⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⢀⣴⡿⠋⠙⠛⠛⠛⠛⠛⠁
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣾⡿⠋⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⢾⠿⠋⠀
//