from itertools import product
from bisect import bisect_left, bisect_right

N = int(input())
S = [list(input()) for _ in range(N)]

mikakutei = []
for i in range(N):
    for j in range(i + 1, N):
        if S[i][j] == '-':
            mikakutei.append((i, j))

for i in range(N):
    for j in range(N):
        if S[i][j] == 'o':
            S[i][j] = 1
        elif S[i][j] == 'x':
            S[i][j] = 0

M = len(mikakutei)
ans = []
for pat in product([0, 1], repeat=M):

    # S の塗り替え
    for k in range(M):
        # mikakutei[k]
        i, j = mikakutei[k]
        # pat[k] で塗る
        S[i][j] = pat[k]
        # 対応する試合も塗る
        S[j][i] = 1 - pat[k]

    # 集計
    cnt = []
    memo = 0
    for i in range(N):
        sub = S[i].count(1)
        if i == 0:
            memo = sub
        cnt.append(sub)
    cnt.sort()
    juni = N - bisect_right(cnt, memo) + 1
    ans.append(juni)

    # S の戻し
    for k in range(M):
        # mikakutei[k]
        i, j = mikakutei[k]
        # pat[k] で塗る
        S[i][j] = '-'

print(min(ans))