N,M = list(map(int, input().split()))
S = []
for _ in range(N):
    S.append(input())
from collections import defaultdict
dict = defaultdict(int)

for i in range(N):
    for j in range(M):
        if S[i][j]=="o":
            dict[j]+=1
minc = 10**10
for v in dict.values():
    minc = min(minc,v)

ans = N-minc+1

print(ans)