#pragma GCC optimize("O2")
#include <algorithm>
#include <array>
#include <bit>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfenv>
#include <cfloat>
#include <chrono>
#include <cinttypes>
#include <climits>
#include <cmath>
#include <compare>
#include <complex>
#include <concepts>
#include <cstdarg>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <new>
#include <numbers>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <ranges>
#include <set>
#include <span>
#include <sstream>
#include <stack>
#include <streambuf>
#include <string>
#include <tuple>
#include <type_traits>
#include <variant>

#define int ll
#define INT128_MAX (__int128)(((unsigned __int128) 1 << ((sizeof(__int128) * __CHAR_BIT__) - 1)) - 1)
#define INT128_MIN (-INT128_MAX - 1)

#define clock chrono::steady_clock::now().time_since_epoch().count()

#ifdef DEBUG
#define dbg(x) cout << (#x) << " = " << x << '\n'
#else
#define dbg(x)
#endif

namespace R = std::ranges;
namespace V = std::views;

using namespace std;

using ll = long long;
using ull = unsigned long long;
using ldb = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
//#define double ldb

template<class T>
ostream& operator<<(ostream& os, const pair<T, T> pr) {
  return os << pr.first << ' ' << pr.second;
}
template<class T, size_t N>
ostream& operator<<(ostream& os, const array<T, N> &arr) {
  for(const T &X : arr)
    os << X << ' ';
  return os;
}
template<class T>
ostream& operator<<(ostream& os, const vector<T> &vec) {
  for(const T &X : vec)
    os << X << ' ';
  return os;
}
template<class T>
ostream& operator<<(ostream& os, const set<T> &s) {
  for(const T &x : s)
    os << x << ' ';
  return os;
}

int solve() {
  int n; cin >> n;
  vector<array<int, 3>> eq(n);
  for(int i = 0, dep = 0; i < n; i++) {
    string s; cin >> s;
    int cnts = 0, cntt = 0;
    for(char c : s)
      cnts += c == 's', cntt += c == 't';
    dep -= s.back() == '}';
    eq[i] = {cntt, dep, -cnts};
    dep += s.back() == '{';
  }

  {
    vector<array<int, 3>> tmp;
    for(auto [a, b, c] : eq) {
      if (b == 0) {
        if (a != 0 or c != 0)
          return -1;
      } else {
        tmp.push_back({a, b, c});
      }
    }
    eq.swap(tmp);
  }

  dbg(eq);

  if (eq.empty())
    return 1;

  for(int x = 1; x <= 2000; x++) {
    bool ok = true;
    int yp = LLONG_MAX;
    for(auto [a, b, c] : eq) {
      int y = (c - a * x) / b;
      if (y >= 0 or a * x + b * y != c) {
        ok = false;
        break;
      }
      if (yp == LLONG_MAX)
        yp = y;
      if (y != yp) {
        ok = false;
        break;
      }
    }
    if (ok)
      return x;
  }

  return -1;
}

signed main() {
  ios::sync_with_stdio(false), cin.tie(NULL);

  cout << solve() << '\n';

  return 0;
}