import sys
input = lambda: sys.stdin.readline().rstrip()

#  -----------------------  #

n, m = map(int, input().split())
S = [input() for _ in range(n)]

ans = 0
for j in range(m):
  cnt = 0
  for i in range(n):
    if S[i][j] == 'x':
      cnt += 1
  ans = max(ans, cnt)
print(ans + 1)