import copy
import itertools
n=int(input())
l=[list(input()) for i in range(n)]
num=[i for i in range(n)]
L=list(itertools.combinations(num,2))
ans=n
for i in range(2**(n*(n-1)//2)):
  l2=copy.deepcopy(l)
  x=format(i,'0'+str(n*(n-1)//2)+'b')
  for j in range(len(x)):
    if l2[L[j][0]][L[j][1]]=='-':
      if x[j]=='1':
        l2[L[j][0]][L[j][1]]='o'
        l2[L[j][1]][L[j][0]]='x'
      else:
        l2[L[j][0]][L[j][1]]='x'
        l2[L[j][1]][L[j][0]]='o'
  win=[]
  for j1 in range(n):
    ct=0
    for j2 in range(n):
      if l2[j1][j2]=='o':
        ct+=1
    win.append(ct)
  y=win[0]
  win=list(set(win))
  win.sort()
  win.reverse()
  ans=min(ans,win.index(y)+1)
print(ans)