import re

first_multiple_input = input().rstrip().split()

n = int(first_multiple_input[0]) m = int(first_multiple_input[1])

matrix = []

for _ in range(n): matrix_item = input() matrix.append(matrix_item[:m])

text = ''.join(matrix) assigned_text=[]

for i in range(m): for j in range(i,len(text),m): assigned_text.append(text[j])

print(re.sub(r'(?<=[0-9a-zA-Z])[!,@,#,$,%,&,\s]+(?=[0-9a-zA-Z])',' ',''.join(assigned_text)))