#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-9;
const ll mod=1e9+7;
const int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

int n;
vvi a;
vi b,c;

int main(){
	cin>>n;
	a=vvi(n,vi(n));
	for(int i=0;i<n;i++) for(int j=0;j<n;j++){
		char C;
		cin>>C;
		if(i<j){
			if(C=='o') a[i][j]++;
			if(C=='x') a[i][j]--;
			b.push_back(i);
			c.push_back(j);
		}
	}
	int res=n,N=b.size();
	for(int i=0;i<1<<N;i++){
		bool B=1;
		vi d(n);
		for(int j=0;j<N;j++){
			if(i&1<<j&&a[b[j]][c[j]]==-1) B=0;
			if(!(i&1<<j)&&a[b[j]][c[j]]==1) B=0;
			if(i&1<<j) d[b[j]]++;
			else d[c[j]]++;
		}
		if(!B) continue;
		set<int> st;
		for(int j=1;j<n;j++) if(d[j]>d[0]) st.insert(d[j]);
		res=min(res,(int)st.size()+1);
	}
	cout<<res<<endl;
}