N,M = map(int,input().split())
S = [input().strip() for _ in range(N)]
for i in range(N):
    s = S[i]
    a = set()
    for j in range(M):
        if s[j]=="o":
            a.add(j)
    S[i] = a
K = 0
A = set([])
Ind = set([])
while len(A)<M:
    amin = 100000
    bmin = set()
    indmin = 0
    for i in range(N):
        if i in Ind:continue
        a = S[i]-A
        if len(a)<amin:
            amin = len(a)
            bmin = a
            indmin = i
    A = A|bmin
    Ind.add(indmin)
    K += 1
print(K)