#include<iostream>

 #include<cstring>

 using namespace std;

 int r,c;///行r，列c

 const int dr[] = {-, ,-, ,-,,-,};

 const int dc[] = {-,-,-,-, ,, ,};

 bool chess[]['Z'+];

 struct square{

 int row;

 char col;

 };

 bool inside(int x,int y)

 {

     return x>= && x<=r && y>='A' && y<='A'+c-;

 }

 bool dfs(square *way,int i,int j,int step)

 {

     chess[i][j]=true;

     way[step].row=i;

     way[step].col=j;

     if(step==r*c)

         return true;

     for(int k=;k<;k++)   //骑士从当前位置尝试跳到其他位置

     {

         int ii,jj;

         ii = i+dr[k];jj = j+dc[k];

         if(!chess[ii][jj] && inside(ii,jj))

             if(dfs(way,ii,jj,step+))

                 return true;

     }

     chess[i][j]=false;  //能执行到这步，说明前面跳的8步都不符合要求

     return false;       //即当前位置是错误位置，擦除记录返回上一步

 }

 int main()

 {

     int n;

     cin>>n;

     for(int i=;i<=n;i++)

     {

         cin>>r>>c;

         bool flag = false;

         memset(chess,false,sizeof(chess));

         square *way = new square[r*c+];

         for(int i='A';i<='A'+c-;i++)

         {

             for(int j=;j<=r;j++)

             {

                 flag = dfs(way,j,i,);

                 if(flag)

                     break;

             }

             if(flag)

                     break;

         }

         ///打印解

         cout<<"Scenario #"<<i<<":"<<endl;

         if(flag)

         {

             for(int k=;k<=r*c;k++)

                         cout<<way[k].col<<way[k].row;

                     cout<<endl<<endl;

         }else{

             cout<<"impossible"<<endl<<endl;

         }

     }

     return ;

 }