#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<string> s(n);
    for(int i=0; i<n; ++i)
        cin >> s[i];

    int m = n * (n - 1) / 2;
    int ret = INT_MAX;
    for(int i=0; i<(1<<m); ++i){
        bitset<32> bs(i);
        int k = 0;

        bool ng = false;
        vector<int> win(n, 0);
        for(int y=0; y<n; ++y){
            for(int x=0; x<y; ++x){
                if(bs[k]){
                    ++ win[y];
                    if(s[y][x] == 'x')
                        ng = true;
                }
                else{
                    ++ win[x];
                    if(s[y][x] == 'o')
                        ng = true;
                }
                ++ k;
            }
        }
        if(ng)
            continue;

        int rank = 1;
        for(int i=n; i>=0; --i){
            if(win[0] == i)
                ret = min(ret, rank);
            if(find(win.begin(), win.end(), i) != win.end())
                ++ rank;
        }
    }
    cout << ret << endl;

    return 0;
}