import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1]
mii = lambda x = " ": [*map(int,inp().split(x))]
mfi = lambda x = " ": [*map(float,inp().split(x))]
ii = lambda : int(inp())
tc, r, c = mii()
for _ in range(tc):
l = [input() for i in range(r)]
d = []
for j in range(c):
for i in range(r):
if l[i][j] == '#':
d.append(i)
print(max(d) - min(d))