#include<stdio.h>
#include<iostream>
#include<algorithm>
#define inf 0X7fffffff
using namespace std;
const int N=1e4+9;
int read(int &x){
    int dat=0,oko=1;char chc=getchar();
    while(chc<'0'||chc>'9'){if(chc=='-')oko=-1;chc=getchar();}
    while(chc>='0'&&chc<='9'){dat=dat*10+chc-'0';chc=getchar();}
    x=dat*oko;return x;
}int T,need,la[N],ra[N],lb[N],rb[N],tota,totb;
int dela,delb,lena,lenb;
string s1,s2;
void solve(){
    cin>>s1>>s2;
    tota=0,totb=0;
    dela=0,delb=0;
    lena=0,lenb=0;
    int last=0;need=s2.length();
    if(s2=="1"&&s1!="1"){
        cout<<"-1\n";return;
    }if(s2!="1"&&s1=="1"){
        cout<<"-1\n";return;
    }for(int i=1;i<=s1.length();i++){
        if(s1[i-1]=='1'){
            lena++;
            if(!last)continue;
            tota++;
            la[tota]=last-dela;
            ra[tota]=i-dela;
            dela+=i-last;
            last=0;
        }else if(!last)last=i;
    }
    if(last&&s1.length()-last>0){
        //cout<<"FLKAJ\n";
        tota++;
        la[tota]=lena+1;
        ra[tota]=lena+1+s1.length()-last;
    }if(last){
        tota++;
        la[tota]=lena;
        ra[tota]=lena+1;lena++;
    }if(lena==1){cout<<"-1\n";return;}
    while(lena>need){
        tota++;
        la[tota]=lena-2;
        ra[tota]=lena-1;
        tota++;
        la[tota]=lena-1;
        ra[tota]=lena+1;
        lena--;
    }//cout<<"lena="<<lena<<"\n";
    while(lena<need){
        tota++;
        la[tota]=lena-1;
        ra[tota]=lena;
        tota++;
        la[tota]=lena-1;
        ra[tota]=lena;
        tota++;
        la[tota]=lena-1;
        ra[tota]=lena+1;
        tota++;
        la[tota]=lena-1;
        ra[tota]=lena;
        tota++;
        la[tota]=lena+1;
        ra[tota]=lena+2;
        lena++;
    }for(int i=s2.length();i>=1;i--){
        if(s2[i-1]=='1')continue;
        tota++;
        la[tota]=i-1;
        ra[tota]=i;
        //printf("ff %d %d\n",i-1,i);
        tota++;
        la[tota]=i;
        ra[tota]=i+1;
        //printf("ff %d %d\n",i,i+1);

    }cout<<tota<<"\n";
    for(int i=1;i<=tota;i++){
        cout<<la[i]<<" "<<ra[i]<<"\n";
    }
}
int main(){
    cin>>T;
    while(T--)solve();
    return 0;
}
/*
1
111111
1111
*/