#define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <clocale>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define IOS ios::sync_with_stdio(false); cin.tie(0);
#define FOR(i, s, n) for(int i = (s), i##_len=(n); i < i##_len; ++i)
#define FORS(i, s, n) for(int i = (s), i##_len=(n); i <= i##_len; ++i)
#define VFOR(i, s, n) for(int i = (s); i < (n); ++i)
#define VFORS(i, s, n) for(int i = (s); i <= (n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define REPS(i, n) FORS(i, 0, n)
#define VREP(i, n) VFOR(i, 0, n)
#define VREPS(i, n) VFORS(i, 0, n)
#define RFOR(i, s, n) for(int i = (s), i##_len=(n); i >= i##_len; --i)
#define RFORS(i, s, n) for(int i = (s), i##_len=(n); i > i##_len; --i)
#define RREP(i, n) RFOR(i, n, 0)
#define RREPS(i, n) RFORS(i, n, 0)
#define ALL(v) (v).begin(), (v).end()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v), greater<decltype(v[0])>())
#define SZ(x) ((int)(x).size())
#define REV(x) reverse(ALL(x))
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end())

using ld = long double;
using ll = long long;
using ui = unsigned int;
using ull = unsigned long long;
using Pi_i = pair<int, int>;
using Pll_ll = pair<ll, ll>;
using VB = vector<bool>;
using VC = vector<char>;
using VD = vector<double>;
using VI = vector<int>;
using VLL = vector<ll>;
using VS = vector<string>;
using VSH = vector<short>;
using VULL = vector<ull>;

const int MOD = 1000000007;
const int INF = 1000000000;
const int NIL = -1;
const double EPS = 1E-10;

template<class T, class S>
bool chmax(T &a, const S &b){
    if(a < b){
        a = b; return true;
    }
    return false;
}
template<class T, class S>
bool chmin(T &a, const S &b){
    if(b < a){
        a = b; return true;
    }
    return false;
}


inline int grayCode(int i){
    return i ^ (i >> 1);
}

inline int invGrayCode(int j){
    for(int k = 0; k < 5; ++k){// 2pow(5) = 32
        j = j ^ (j >> (1<<k));
    }
    return j;
}

unordered_map<int, int> twoPow{{1, 0}, {2, 1}, {4, 2}, {8, 3}, {16, 4}, {32, 5}, {64, 6}, {128, 7}, {256, 8}, {512, 9}, {1024, 10}, {2048, 11}, {4096, 12}, {8192, 13}, {16384, 14}, {32768, 15}, {65536, 16}, {131072, 17}, {262144, 18}, {524288, 19}};
vector<Pi_i> notMatch;
VI score;
int N;

int bitSearch(){
    int n = notMatch.size();
    if(!n){
        int sc = score[0];
        SORT(score);
        UNIQUE(score);
        REV(score);
        REP(i, score.size()){
            if(score[i] == sc) return i + 1;
        }
    }
    int ans = 6, prvj = 0;
    VI sc;
    REP(i, n) ++score[notMatch[i].second];
    REP(i, N) sc.PB(score[i]);
    SORT(sc);
    UNIQUE(sc);
    REV(sc);
    REP(i, sc.size()){
        if(sc[i] == score[0]) ans = i + 1;
    }
    FOR(i, 1, (1 << n)){
        sc.clear();
        int j = grayCode(i);
        int changebit = j ^ prvj;
        int cb = twoPow[changebit];
        if(j & changebit){// changeBit が立った
            ++score[notMatch[cb].first];
            --score[notMatch[cb].second];
        }else{// changeBit がなくなった
            --score[notMatch[cb].first];
            ++score[notMatch[cb].second];
        }
        REP(i, N) sc.PB(score[i]);
        SORT(sc);
        UNIQUE(sc);
        REV(sc);
        REP(i, sc.size()){
            if(sc[i] == score[0]) chmin(ans, i+1);
        }
        prvj = j;
    }
    return ans;
}


int main(){
    cin >> N;
    score.resize(N, 0);
    string s;
    REP(i, N){
        cin >> s;
        FOR(j, i+1, N){
            if(s[j] == 'o') ++score[i];
            else if(s[j] == 'x') ++score[j];
            else notMatch.PB({i, j});
        }
    }
    cout << bitSearch() << endl;
    return 0;
}