#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
template <class... T> void dbg(T... x) { char e{}; ((cerr << e << x, e = ' '), ...); }
template <class T> void org(T l, T r) { while (l != r) cerr << ' ' << *l++; cerr << '\n'; }
#define debug(x...) dbg(#x, '=', x, '\n')
#define olist(x...) dbg(#x, '='), org(x)
#else
#define debug(...) ((void)0)
#define olist(...) ((void)0)
#endif
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define ff first
#define ss second

using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;
using Pt = pair<int, int>;

template <class T> inline constexpr T inf = numeric_limits<T>::max() / 2;
constexpr int mod = 1e9 + 7;

template<class T> bool chmin(T &a, T b) { return (b < a and (a = b, true)); }
template<class T> bool chmax(T &a, T b) { return (a < b and (a = b, true)); }
template<class... T> int add(T... x) { int t{}; return (((t += x) %= mod), ...), t; }
template<class... T> int mul(T... x) { i64 t{1}; return (((t *= x) %= mod), ...), t; }

void solve() {
    int n;
    cin >> n;

    vector<array<int, 3>> E(n);

    int dep = 0;
    for (int i = 0; i < n; i++) {
        string line;
        cin >> line;

        for (char c : line) {
            if (c == '}') dep--;
            if (c == 's') E[i][0]++;
            if (c == 't') E[i][1]++;
        }

        E[i][2] = dep;
        
        for (char c : line) {
            if (c == '{') dep++;
        }
        
    }

    auto sol = [&](int k) -> int {
        int x = inf<int>;
        bool f = false;
        for (auto [a, b, c] : E) {
            if (!b) {
                if (a != c * k) return inf<int>;
                continue;
            }
            f = true;
            if ((c * k - a) % b) return inf<int>;
            int t = (c * k - a) / b;
            if (x == inf<int>) x = t;
            if (x != t) return inf<int>;
        }
        if (!f) return 1;
        if (x == 0) return inf<int>;
        return x;
    };

    int ans = inf<int>;
    if (sol(0) != inf<int>) ans = 1;
    for (int i = 1; i < 5000; i++) {
        chmin(ans, sol(i));
    }

    cout << (ans == inf<int> ? -1 : ans) << '\n';
}

signed main() {
    cin.tie(0)->sync_with_stdio(false);
    cin.exceptions(cin.failbit);
    int T = 1;
    // cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}