#include <iostream>
using namespace std;
const int N = 30;

int n, p, q;
bool res[N][N];
bool succ;

int dx[8] = {1, 1, -1, -1, 2, 2, -2, -2};
int dy[8] = {2, -2, 2, -2, 1, -1, 1, -1};

struct Loc
{
    int x;
    char y;
}loc[N];

void dfs(int a, int b, int idx)
{
    loc[idx].x = a;
    loc[idx].y = b + 'A' - 1;

    if(idx == p * q)
    {
        succ = 1;
    }

    for(int i = 0; i < 8; i++)
    {
        int x = a + dx[i], y = b + dy[i];
        if(x > 0 && x <= p && y > 0 && y <= q && res[x][y] == 0)
        {
            res[x][y] = 1;
            dfs(x, y, idx + 1);
            res[x][y] = 0;
        }
    }
}

int main()
{
    cin >> n;
    for(int i = 1; i <= n; i++)
    {
        cin >> p >> q;
        for(int i = 0; i < N; i++)
        {
            for(int j = 0; j < N; j++)
            {
                res[i][j] = 0;
            }
        }
        res[1][1] = 1;
        succ = 0;
        dfs(1, 1, 1);

        cout << "Scenario #" << i << ":" << endl;
        if(succ == 1) 
        {
            for(int i = 1; i <= p * q; i++)
            {
                cout << loc[i].y << loc[i].x ;
            }
            cout << endl;
        }
        else
        {
            cout << "impossible" << endl;
        }
        if(i != n) cout << endl;
    }
    return 0;
}