import sys,copy
input=lambda:sys.stdin.readline().rstrip()
N=int(input())
ans=6
wins=[0 for i in range(N)]
pairs=[]
for i in range(N):
	S=input()
	for j in range(i):
		if S[j]=='o':
			wins[i]+=1
		elif S[j]=='x':
			wins[j]+=1
		else:
			pairs.append([i,j])
for i in range(1<<len(pairs)):
	temp=copy.copy(wins)
	for j in range(len(pairs)):
		temp[pairs[j][(i>>j)&1]]+=1
	ans=min(ans,sorted(list(set(temp)))[::-1].index(temp[0])+1,ans)
print(ans)