#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int dfs(int n, string a[], int t) {
    if (t == 0) {
        int wins[n] {};
        for (int i=0;i<n;i++)
            for (char c : a[i])
                if (c=='o') wins[i]++;
        bool used[n] {};
        int rank = 1;
        for (int i=1;i<n;i++)
            if (wins[0] < wins[i] && !used[wins[i]]) {
                rank++;
                used[wins[i]] = true;
            }
        return rank;
    }
    for (int i=0;i<n;i++)
        for (int j=0;j<n;j++) {
            if (a[i][j] != '-') continue;
            a[i][j] = 'o'; a[j][i] = 'x';
            int r1 = dfs(n, a, t-1);
            a[i][j] = 'x'; a[j][i] = 'o';
            int r2 = dfs(n, a, t-1);
            a[i][j] = '-'; a[j][i] = '-';
            return min(r1, r2);
        }
    return -1;
}

int main() {
    int n;
    cin >> n;
    string a[n];
    int t = 0;
    for (int i=0;i<n;i++) {
        cin >> a[i];
        for (char c : a[i]) if (c=='-') t++;
    }
    cout << dfs(n, a, t/2) << endl;
    return 0;
}