#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000



int main(){
	
	int N;
	cin>>N;
	
	vector<string> S(N);
	rep(i,N){
		cin>>S[i];
	}
	
	vector<pair<int,int>> p;
	rep(i,N){
		for(int j=i+1;j<N;j++){
			p.emplace_back(i,j);
		}
	}
	int ans = Inf;
	
	rep(i,1<<p.size()){
		bool f = true;
		vector<int> win(N,0);
		rep(j,p.size()){
			char c = S[p[j].first][p[j].second];
			if(c=='o'&&((i>>j)&1)==0)f = false;
			if(c=='x'&&((i>>j)&1)==1)f = false;

			if((i>>j)&1){
				win[p[j].first]++;
			}
			else{
				win[p[j].second]++;
			}
		}
		if(!f)continue;
		auto ww = win;
		sort(ww.begin(),ww.end());
		ww.erase(unique(ww.begin(),ww.end()),ww.end());
		ans = min(ans,(int)distance(lower_bound(ww.begin(),ww.end(),win[0]),ww.end()));
	}
	cout<<ans<<endl;
	
	return 0;
}