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

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  int n;
  cin >>n;
  vector<int> spaces(n), tabs(n), indent(n);
  for (int i =0; i < n; i++) {
    string s;
    cin >> s;
    int l = (int)s.size();
    for (int j = 0; j+1<l; j++) {
      spaces[i] += (s[j] == 's');
      tabs[i] += (s[j] == 't');
    }
    if (s[l-1] == '{') {
      if (i) indent[i] += indent[i-1]+1;
    } else if (s[l-1] == '}') {
      if (i && i+1 < n) {
        indent[i] += indent[i-1];
        indent[i+1] += -1;
      }
    } else assert(false);
  }

  const int MAX_CHECK = 3e6;
  int ans = -1;
  for (int width = 1; width <= MAX_CHECK; width++) {
    bool ok = true;
    int64_t mult = -1;
    for (int i = 0; i < n; i++) {
      int64_t tot_width = int64_t(tabs[i])*width + spaces[i];
      if (indent[i]) {
        if (tot_width%indent[i] != 0) {
          ok = false;
          break;
        }
        int64_t this_mult = tot_width/indent[i];
        if (mult != -1 && mult != this_mult) {
          ok = false;
          break;
        }
        mult = this_mult;
      } else if (tot_width != 0) {
        ok = false;
        break;
      }
    }
    if (!ok) continue;
    ans = width;
    break;
  }
  cout << ans << '\n';
}