#include <bits/stdc++.h>
using namespace std;
#define int long long 
bool solve(string s1,string s2,vector<pair<int,int>> &ans)
{
    ans.clear();
    int n=(int)s1.size(),m=(int)s2.size();
    auto f= [&](int l,int r){
        int g=0;
        // cout<<"l="<<l<<" r="<<r<<" n="<<n<<"\n";
        // assert(l<=r&&r<=(int)s1.size()-1);
        assert(r<=n);
        ans.emplace_back(l,r);
        for(int i=l;i<=r;i++)g=g*3+s1[i]-'0';
        string s=s1.substr(0,l);
        string st;
        do{
            st.push_back(char('0'+g%2));g/=2;
        }while(g>0);
        reverse(st.begin(),st.end());
        // cout<<"l="<<l<<" r="<<r<<"\n";
        // cout<<"pr="<<s1.substr(l,r-l+1)<<"\n";
        // cout<<"now="<<st<<"\n";
        s.append(st);
        s.append(s1.substr(r+1));
        s1=s;
        n=(int)s1.size()-1;
    };
    auto f1 = [&](int l,int r){// 11 -> 10
        f(l,l+1);
        f(l+1,l+2);
    };
    auto f2 = [&](int l,int r){// 111 -> 11
        f(l,l+1);
        f(l+1,l+3);
    };
    auto f3 = [&](int l,int r){// 11 -> 111
        f(l,r);
        f(l,l+1);
        f(l+1,l+2);
    };
    auto f4 = [&](int l,int r){// 11 - > 101
        f(l,r);
        f(l,l+2);
        f(l+1,l+2);
    };
    auto f5 = [&](int l,int r){// 10 -> 100
        f(l,r);
        f(l,r);
    };
    auto f6 = [&](int l,int r){// 11 -> 110
        f(l,r);
        f(l,l+1);
    };
    /*-----------------------------*/
    if(s2=="1"){
        if(s1!=s2)return false;
        return true;
    }
    if(s1=="1")return false;
    /*-----------------------------*/
    s1="x"+s1;
    s2="x"+s2;
    while(s1.size()>3){
        // cout<<"???\n";
        // cout<<s1<<"\n";
        if(s1[2]=='1'){
            f(1,2);
            f(2,4);
        }
        else{
            f(2,3);
        }
    }
    if(s1[2]=='0')f(1,2);
    assert(s1=="x11");
    // cout<<"?ijosefoiweifo\n";
    int cnt=0;
    for(int i=1;i<=m;i++)cnt+=s2[i]-'0';
    if(cnt==1){
        f1(1,2);
        assert(s1=="x10");
        while(s1.size()<s2.size())f5(1,2);
        return true;
    }
    else{
        while((int)s1.size()-1<cnt){
            f3(n-1,n);
        }
        vector<int> v;
        int now=0;
        for(int i=m;i>=1;i--){
            if(s2[i]=='1'){
                v.push_back(now);
                now=0;
            }
            else now++;
        }
        reverse(v.begin(),v.end());
        for(int i=cnt;i>=1;i--){
            int now=v[i-1];
            if(now==0)continue;
            // cout<<"i="<<s1<<" "<<s2<<"\n";
            if(i==cnt){
                f6(i-1,i);
                now--;
                while(now--)f5(i,i+1);
            }
            else{
                f4(i,i+1);
                now--;
                while(now--)f5(i,i+1);
            }
        }
        // cout<<"s1="<<s1<<"\n";
        // cout<<"s2="<<s2<<"\n";
        assert(s1==s2);
        return true;
    }

}
string gen()
{
    string s="1";
    int n=rand()%30;
    while(n--)s.push_back(char('0'+rand()%2));
    return s;
}
signed main()
{
    srand(time(NULL));

    ios::sync_with_stdio(false);
    cin.tie(0);
    int T;cin>>T;
    // int T=100;
    while(T--){
        vector<pair<int,int>> ans;
        // cout<<solve()<<"\n";
        string s1,s2;cin>>s1>>s2;
        // string s1=gen(),s2=gen();
        if(!solve(s1,s2,ans))cout<<-1<<"\n";
        else{
            assert((int)ans.size()<=512);
            cout<<ans.size()<<"\n";
            for(auto [x,y]:ans)cout<<x<<" "<<y<<"\n";
        }
    }
}
/*
3
1
111
110110
1101010
1111
111111

1
110110
1101010
*/