N = int(input())
s = [input() for _ in range(N)]
win_num = {i: 0 for i in range(N)}
unmatch = []

for i in range(N):
    for j in range(i+1, N):
        if s[i][j] == 'o':
            win_num[i] += 1
        elif s[i][j] == 'x':
            win_num[j] += 1
        else:
            if i == 0:
                win_num[i] += 1
            else:
                unmatch.append((i, j))
    
l = len(unmatch)
ans = 10 ** 18

for i in range(2 ** l):
    win_num_copy = win_num.copy()
    
    for j in range(l):
        if (i >> j) & 1:
            win_num_copy[unmatch[j][0]] += 1
        else:
            win_num_copy[unmatch[j][1]] += 1
    
    for i, value in enumerate(sorted(list(set(win_num_copy.values())), reverse=True), 1):
        if win_num_copy[0] == value:
            ans_cand = i
    
    ans = min(ans, ans_cand)

print(ans)