def cul(r):
    res = 0
    for i in r:
        if i == "o":
            res += 1

    return res


def main():
    n = int(input())
    s = [list(input()) for i in range(n)]

    score = [0] * n
    uncertain = []
    for i in range(n):
        for j in range(i+1, n):
            if s[i][j] == "-":
                uncertain.append((i, j))

    ans = n
    for i in range(2**len(uncertain)):
        for j in range(len(uncertain)):
            k, l = uncertain[j]
            if (i >> j) & 1:
                s[k][l], s[l][k] = "o", "x"
            else:
                s[k][l], s[l][k] = "x", "o"

        cnt, sc, score[0] = 1, set(), cul(s[0])
        for j in range(1, n):
            score[j] = cul(s[j])
            if score[0] < score[j] and score[j] not in sc:
                cnt += 1
                sc.add(score[j])

        ans = min(ans, cnt)

        for j in range(len(uncertain)):
            k, l = uncertain[j]
            s[k][l] = s[l][k] = "-"

    print(ans)


if __name__ == '__main__':
    main()