#include <iostream>
#include <vector>
#include <string>
using namespace std ;
int main() {
   int n, glev = 0, r = -1 ;
   string st ;
   cin >> n ;
   vector<int> t(n), s(n), lev(n) ;
   for (int i=0; i<n; i++) {
      cin >> st ;
      glev -= (st[st.size()-1] == '}') ;
      for (auto c: st)
         c == 's' ? s[i]++ : c == 't' ? t[i]++ : 0 ;
      lev[i] = glev ;
      glev += (st[st.size()-1] == '{') ;
   }
   for (int tv=1; r < 0 && tv<10000; tv++) {
      int k = -1, good = 1 ;
      for (int i=0; good && i<n; i++) {
         int ind = s[i] + t[i] * tv ;
         if (lev[i] == 0 && ind == 0)
            continue ;
         if ((lev[i] == 0 && ind) || (lev[i] != 0 && ind == 0) ||
             ind % lev[i] != 0 || (k >= 0 && ind / lev[i] != k))
            good = 0 ;
         else
            k = ind / lev[i] ;
      }
      if (good)
         r = tv ;
   }
   cout << r << endl ;
}