h, w = map(int, input().split())
s = [input() for _ in range(h)]
a = 1e5
for i in s:
	c = 0
	for j in i:
		if j == '.' and c != 0:
			a = min(a, c)
			c = 0
		if j == '#':
			c += 1
	if c != 0:
		a = min(a, c)
for i in range(w):
	c = 0
	for j in range(h):
		k = s[j][i]
		if k == '.' and c != 0:
			a = min(a, c)
			c = 0
		if k == '#':
			c += 1
	if c != 0:
		a = min(a, c)
print(a)