local n, m = io.read("*n", "*n", "*l")
local s = {}
for i = 1, n do
  s[i] = io.read()
end
local r = 0
for i = 1, m do
  local c = 1
  for j = 1, n do
    if s[j]:sub(i, i) == "x" then c = c + 1 end
  end
  r = math.max(r, c)
end
print(r)