from re import sub


n, m = map(int, input().split())

matrix = [""] * m
line = ""
pattern = r"[a-zA-Z0-9][^a-zA-Z0-9]+[a-zA-Z0-9]"

for _ in range(n):
    line = input()
    for i in range(m):
        matrix[i] += line[i]

def replace(match):
    return f"{match.group(0)[0]} {match.group(0)[-1]}"

print(sub(pattern, replace, "".join(matrix)))