如果骑士可以走完所有格子，那一定可以走到a1，所以我们从a1开始深搜

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

int path[88][88], vis[88][88], p, q, cnt;
bool flag;
//8种走法
int dx[8] = {
    
     -1, 1, -2, 2, -2, 2, -1, 1 };
int dy[8] = {
    
     -2, -2, -1, -1, 1, 1, 2, 2 };
//判断该点是否符合要求
bool judge(int x, int y)
{
    
    
    if (x >= 1 && x <= p && y >= 1 && y <= q && !vis[x][y] && !flag)
        return true;
    return false;
}

void DFS(int r, int c, int step)
{
    
    
    path[step][0] = r;//记录路径
    path[step][1] = c;
    if (step == p * q)
    {
    
    
        flag = true;
        return;
    }
    for (int i = 0; i < 8; i++)
    {
    
    
        int nx = r + dx[i];
        int ny = c + dy[i];
        if (judge(nx, ny))
        {
    
    

            vis[nx][ny] = 1;
            DFS(nx, ny, step + 1);
            vis[nx][ny] = 0;
        }
    }
}

int main()
{
    
    
    int i, j, n, cas = 0;
    scanf("%d", &n);
    while (n--)
    {
    
    
        flag = 0;
        scanf("%d%d", &p, &q);
        memset(vis, 0, sizeof(vis));
        vis[1][1] = 1;
        DFS(1, 1, 1);
        printf("Scenario #%d:\n", ++cas);
        if (flag)
        {
    
    
            for (i = 1; i <= p * q; i++)
                printf("%c%d", path[i][1] - 1 + 'A', path[i][0]);
        }
        else
            printf("impossible");
        printf("\n");
        if (n != 0)
            printf("\n");
    }
    return 0;
}