#include <iostream>
#include <vector>

using namespace std;

int main() {
  int n;
  cin >> n;
  vector<int> tv(n), sv(n), depth(n);
  int d = 0;
  for(int i = 0; i < n; i++) {
    string s;
    cin >> s;
    for(int a = 0; a + 1 < s.size(); a++) {
      (s[a] == 't' ? tv[i] : sv[i])++;
    }
    if(s.back() == '{') depth[i] = d++;
    else depth[i] = --d;
  }
  int ans = -1;
  for(int ret = 1; ans < 0 && ret <= 10000; ret++) {
    int k = -1;
    for(int i = 0; i < n; i++) {
      if(tv[i] > 0 || sv[i] > 0) {
        int amt = tv[i] * ret + sv[i];
        if(amt % depth[i]) k = 0;
        else k = amt / depth[i];
        break;
      }
    }
    if(k == -1) {
      ans = 1;
      break;
    }
    bool good = true;
    for(int i = 0; good && i < n; i++) good = tv[i] * ret + sv[i] == depth[i] * k;
    if(good) ans = ret;
  }
  cout << ans << "\n";
}