#include <stdio.h>
#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <stack>
#include <algorithm>
#include <iomanip>
#include <map>
#include <queue>
#include <functional>
#include <numeric>
#include <chrono>
#include <cstdlib>
using ll = long long;
using namespace std;

const ll MOD = 1e9 + 7;
#define REP(i, n) for (int(i) = 0; (i) < (n); ++(i))
#define repi(i, a, b) for (int i = int(a); i < int(b); ++i)
// bool operator<(const pair<int, int> &a, const pair<int, int> &b)
// {
//     if (a.first == b.first)
//         return a.second < b.second;
//     return a.first < b.first;
// };

/*unsigned int xor128(void)
{
    static unsigned int x = 123456789, y = 362436069, z = 521288629, w = 88675123;
    unsigned int t = (x ^ (x << 11));
    x = y;
    y = z;
    z = w;
    return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
unsigned int xor128rnd(unsigned int m)
{
    return xor128() % m;
}*/

/*bool operator<(const pair<int, int> &a, const pair<int, int> &b)
{
    if (a.first == b.first)
    {
        return a.second < b.second;
    }
    return a.first < b.first;
}*/

int ans = 1000000;
int N;
vector<string> v;
int cnt = 0;
void dfs(int a, int b)
{
    cnt++;
    if (a == N)
    {

        vector<int> vec(N);
        for (int i = 0; i < N; ++i)
        {
            for (int j = 0; j < N; ++j)
            {
                if (v[i][j] == 'o')
                    vec[i]++;
            }
            //cout << vec[i] << endl;
        }
        //cout << endl;
        int t = vec[0];

        sort(v.begin(), v.end());
        vec.erase(unique(vec.begin(), vec.end()), vec.end());
        for (int i = 0; i < (int)vec.size(); ++i)
        {
            if (vec[i] == t)
            {
                ans = min(ans, (int)vec.size() - i);
                break;
            }
        }
        return;
    }

    if (b == N)
    {
        dfs(a + 1, 0);
        return;
    }

    if (v[a][b] != '-')
    {
        dfs(a, b + 1);
        return;
    }
    v[a][b] = 'o';
    v[b][a] = 'x';
    dfs(a, b + 1);
    v[a][b] = 'x';
    v[b][a] = 'o';
    dfs(a, b + 1);
    v[a][b] = v[b][a] = '-';
}
int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> N;

    for (int i = 0; i < N; ++i)
    {
        string s;
        cin >> s;
        v.push_back(s);
    }

    dfs(0, 0);
    cout << ans << endl;
    return 0;
}