TC = int(input())

for tc in range(1, TC+1):
    N, M = map(int, input().split())
    result = []

    #가로줄 확인
    Garo_lst = []
    for i in range(N):
        Data = input()
        Garo_lst.append(Data)
        for i in range(len(Data)-M+1):
            if Data[i:M+i] == Data[i:M+i][::-1]:
                result.append(Data[i:M+i])

    #세로줄 확인
    Sero_lst = []
    Sero_sub_lst = ''
    for x in range(N):
        for y in Garo_lst:
            Sero_sub_lst += y[x]
        Sero_lst.append(Sero_sub_lst)
        Sero_sub_lst =''
    print(Sero_lst)

    for sero_data in Sero_lst:
        for j in range(len(sero_data)-M+1):
            if sero_data[j:M+j] == sero_data[j:M+j][::-1]:
                result.append(sero_data[j:M+j])

    # print(result)
    print("#%d %s"%(tc, result[0]))