import re

n, m = input().strip().split()

tt = []

ss = []

for _ in range(int(n)):

itm = input()

tt.append(itm)

res = "".join(tt)

for nm in range(int(m)):

for th in range(nm, len(res), int(m)):

    ss.append(res[th])

fin = re.sub(r"[!,@,#,$,%,&]+(?=([A-z0-9]))", " ", "".join(ss)) print(fin)