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

write = lambda x: sys.stdout.write(x+"\n"); writef = lambda x: print("{:.12f}".format(x))
debug = lambda x: sys.stderr.write(x+"\n")
YES="Yes"; NO="No"; pans = lambda v: print(YES if v else NO); inf=10**18
LI = lambda : list(map(int, input().split()))
def dlist(*l, fill=0):
    if len(l)==1:
        return [fill]*l[0]
    ll = l[1:]
    return [dlist(*ll, fill=fill) for _ in range(l[0])]
sys.setrecursionlimit(3*10**5+10)

n,m = list(map(int, input().split()))
count = [0]*m
for i in range(n):
    s = input()
    for j in range(m):
        if s[j]=="x":
            count[j] += 1
ans = max(count) + 1
print(ans)