#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
int t;
cin>>t;
while(t--)
{
ll i,j,k,l,m,n,sum=0,f=0;
cin>>n;
string s1,s2;
cin>>s1>>s2;
map <char,int> mp1,mp2,index1,index2;
for(i=0;i<n;i++)
{
index1[s1[i]]=i;
index2[s2[i]]=i;
mp1[s1[i]]++;
mp2[s2[i]]++;
}
for(i=0;i<n;i++)
{
if(mp1[s2[i]]<1 || s1[i]<s2[i])
{
f=1;
}
}
if(f==1)
cout<<-1<<endl;
else
{
vector <int> arr[n+1];
int o=0;
for(i=0;i<n;i++)
{
if(s1[i]!=s2[i])
{
char ch=s2[i];
for(j=0;j<n;j++)
{
if(s2[j]==ch || s1[j]==ch)
{
arr[o].push_back(j);
s1[j]=ch;
}
}
o++;
}
}
cout<<o<<endl;
for(i=0;i<o;i++)
{
cout<<arr[i].size()<<" ";
for(j=0;j<arr[i].size();j++)
{
cout<<arr[i][j]<<" ";
}cout<<endl;
}
}
}
}
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