String - 회문

for tc in range(1,int(input())+1):
    N, M = map(int,input().split())#NxN, 길이 M의 회문
    arr=[list(map(str,input())) for _ in range(N)]
    
    for i in range(N):
        for j in range(N-M+1):
            garo=arr[i][j:j+M]
            sero=[ arr[x][i] for x in range(j,j+M)]
            
            
            if garo== garo[::-1]:
                res=garo
            elif sero == sero[::-1]:
                res=sero
            
            
    res=''.join(res)
    print(f'#{tc} {res}')