import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

n,m = na()
a = [input() for i in range(n)]
ans = 0
for i in range(m):
    s = 0
    for j in range(n):
        if a[j][i] == "x":
            s += 1
    ans = max(ans, s+1)
print(ans)