680 B | 680 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
BLANK = " "
#inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
N, H, W = mii()
l = [input() for _ in range(H)]
for i in range(N):
chk = "?"
for h in range(H):
for w in range(W):
if l[h][W * i + w] != '?':
chk = l[h][W * i + w]
p(end=chk)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()