#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

using namespace std;

#define REP(i,first,last) for (int i=first;i<last;i++)

int N;
char game_results[6][6];
int answer = 10000;

void calc(vector<int> win_count){
  int win_0 = win_count[0];
  int rank = 1;
  sort(win_count.begin()+1, win_count.end());
  REP(i,1,6){
    if (win_count[i] > win_0 && win_count[i-1] != win_count[i]) {
      rank++;
    }
  }
  answer = (rank < answer) ? rank : answer;
}

void solve(int x, int y, vector<int> win_count){
  if (x >= N) {
    y++;
    if (y >= N) {
      return calc(win_count);
    }
    x = y;
  }
  if (game_results[y][x] == 'o') {
    win_count[y]++;
    solve(x+1, y, win_count);
  } else if (game_results[y][x] == 'x') {
    win_count[x]++;
    solve(x+1, y, win_count);
  } else {
    win_count[y]++;
    solve(x+1, y, win_count);
    win_count[y]--;
    win_count[x]++;
    solve(x+1, y, win_count);
  }
}

int main(){
  cin >> N;
  char val;
  REP(i,0,6){
    scanf("%s", game_results[i]);
  }
  vector<int> win_count(6,0);
  solve(0,0,win_count);
  cout<<answer<<endl;
}