#include<bits/stdc++.h>
using namespace std;

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

#define mygc(c) (c)=getchar_unlocked()
#define mypc(c) putchar_unlocked(c)

#define ll long long
#define ull unsigned ll

void reader(int *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
void reader(int *x, int *y){reader(x);reader(y);}
void reader(int *x, int *y, int *z){reader(x);reader(y);reader(z);}
void reader(ll *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
int reader(char c[]){int i,s=0;for(;;){mygc(i);if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF) break;}c[s++]=i;for(;;){mygc(i);if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF) break;c[s++]=i;}c[s]='\0';return s;}

void writer(int x, char c){int s=0,m=0;char f[10];if(x<0)m=1,x=-x;while(x)f[s++]=x%10,x/=10;if(!s)f[s++]=0;if(m)mypc('-');while(s--)mypc(f[s]+'0');mypc(c);}
void writer(ll x, char c){int s=0,m=0;char f[20];if(x<0)m=1,x=-x;while(x)f[s++]=x%10,x/=10;if(!s)f[s++]=0;if(m)mypc('-');while(s--)mypc(f[s]+'0');mypc(c);}
void writer(const char c[]){int i;for(i=0;c[i]!='\0';i++)mypc(c[i]);}

int res = 1000;
int N;
char mp[100][100];

void solve(int a, int b){
  int i, j, k, m;
  int cnt[10], used[10];

  if(a==N){
    rep(i,N) cnt[i] = 0;
    rep(i,N) rep(j,N) if(mp[i][j]=='o') cnt[i]++;
    rep(i,N+1) used[i] = 0;
    k = 1;
    REP(i,1,N) if(cnt[0] < cnt[i]) {
      if(!used[cnt[i]]) k++;
      used[cnt[i]]++;
    }
    res = min(res, k);
    return;
  }

  if(b==N){
    solve(a+1, 0);
    return;
  }

  if(mp[a][b]!='-'){
    solve(a, b+1);
    return;
  }

  mp[a][b] = 'o'; mp[b][a] = 'x'; solve(a, b+1);
  mp[a][b] = 'x'; mp[b][a] = 'o'; solve(a, b+1);
  mp[a][b] = mp[b][a] = '-';
}

int main(){
  int i, j, k;

  reader(&N);
  rep(i,N) reader(mp[i]);

  solve(0,0);

  writer(res,'\n');

  return 0;
}