n,m = map(int,input().split())
s = [input() for i in range(n)]
L = []
for i in range(n):
k = ""
for j in range(m):
if s[i][j] == "#":
if k !="" and len(k) >1:
L.append(k)
k = ""
else:
k+=s[i][j]
if k!="" and len(k) >1:
L.append(k)
for j in range(m):
k = ""
for i in range(n):
if s[i][j] == "#":
if k !="" and len(k) >1:
L.append(k)
k = ""
else:
k+=s[i][j]
if k!="" and len(k) >1:
L.append(k)
L.sort()
print(L[0])