#include<bits/stdc++.h>
using namespace std;
struct node{
	int x,y;
};
int T,n,m,n1,n2;
string a,b,one="1";
vector<node> ans;
vector<int> p;
bool havezero(string s)
{
	int len=s.size();
	for(int i=0;i<len;i++) if(s[i]=='0') return true;
	return false;
}
string deletezero(string s)
{
	int len=s.size();string res="";
	for(int i=0,j;i<len;i++)
	{
		if(s[i]=='0')
		{
			for(j=i+1;j<len&&s[j]=='0';j++);
			if(j==len)
			{
				ans.push_back({i,j-1});
				ans.push_back({i-1,i});
				for(int k=0;k<i;k++) res+="1";
			}
			else
			{
				ans.push_back({i,j});
				for(int k=0;k<i;k++) res+="1";
				for(int k=j;k<len;k++) res+=s[k];
			}
			return res;
		}
	}
}
string addone(string s)
{
	ans.push_back({0,1});
	ans.push_back({0,1});
	ans.push_back({1,2});
	return s+"1";
}
string delone(string s)
{
	ans.push_back({0,1});
	ans.push_back({1,3});
	s.pop_back();
	return s;
}
void addzerotofront()
{
	ans.push_back({0,1});
	ans.push_back({0,1});
	return;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	cin>>T;
	while(T--)
	{
		cin>>b>>a;n1=0;
		n=a.size();m=b.size();p.clear();ans.clear();
		if(a==one&&b==one) {cout<<"0\n";continue;}
		else if(a==one||b==one) {cout<<"-1\n";continue;}
		for(int i=0,j;i<n;)
		{
			n1++;
			for(i++,j=0;i<n&&a[i]=='0';i++,j++);
			p.push_back(j);
		}
		while(havezero(b)) b=deletezero(b);
		m=n2=b.size();
		if(n1==1)
		{
			while(n2>2) b=delone(b),n2--;
			if(p[0]==1)
			{
				ans.push_back({0,1});
				ans.push_back({1,2});
			}
			else
			{
				ans.push_back({0,1});
				for(int i=2;i<p[0];i++) addzerotofront();
			}
		}
		else
		{
			while(n1>n2) b=addone(b),n2++;
			while(n1<n2) b=delone(b),n2--;
			for(int i=n1-1;i>=1;i--)
			{
				if(!p[i]) continue;
				ans.push_back({i-1,i});
				for(int j=2;j<p[i]+1;j++)
				{
					ans.push_back({i-1,i});
					ans.push_back({i-1,i});
				}
				ans.push_back({i-1,i});
			}
			if(p[0])
			{
				ans.push_back({0,1});
				ans.push_back({0,2});
				if(p[0]==1) ans.push_back({1,2});
				else
				{
					for(int i=2;i<p[0];i++) addzerotofront();
				}
			}
		}
		cout<<ans.size()<<"\n";
		for(auto i:ans) cout<<i.x+1<<" "<<i.y+1<<"\n";
	}
	return 0;
}
/*
3
1
111
110110
1101010
1111
111111
*/