#include <bits/stdc++.h>
#ifdef LOCAL
#define debug(...) 42
// #include "cp_debug.h"
#else
#define debug(...) 42
#endif
#define rep(i,a,b) for(int i = a; i < b; ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
using namespace std;
#define int long long

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;

template<typename T> void read(T &x){
    x = 0;char ch = getchar();ll f = 1;
    while(!isdigit(ch)){if(ch == '-')f*=-1;ch=getchar();}
    while(isdigit(ch)){x = x*10+ch-48;ch=getchar();}x*=f;
}
template<typename T, typename... Args> void read(T &first, Args& ... args) {
    read(first);
    read(args...);
}
template<typename T> void write(T x) {
    if(x > 9) write(x/10);
    putchar(x%10 + '0');
}

void solve() {
    int n;
    read(n);
    vi dep(n, -1), ns(n, 0), nt(n, 0);
    int cdep = 0;
    rep(i,0,n) {
        string s;
        cin >> s;
        char end = s.back();
        if(end == '{') {
            dep[i] = cdep;
            cdep++;
        } else {
            assert(end == '}');
            cdep--;
            dep[i] = cdep;
        }
        assert(cdep >= 0);
        s.pop_back();
        for(auto c: s) {
            if(c == 's') {
                ns[i]++;
            } else if(c == 't') {
                nt[i]++;
            } else {
                assert(false);
            }
        }
    }
    assert(ns[0] == 0 && nt[0] == 0 && dep[0] == 0);
    assert(ns[n-1] == 0 && nt[n-1] == 0 && dep[n-1] == 0);
    if(n == 2) {
        cout<<1<<'\n';
        return;
    }

    int base_s = -1, base_t = -1, ans = -1;
    rep(i,0,n) if(dep[i]==1) {
        base_s = ns[i];
        base_t = nt[i];
        break;
    }
    if(base_s == -1 || base_t == -1) {
        assert(base_s == -1 && base_t == -1);
        rep(i,0,n) {
            assert(dep[i] == 0);
            if(ns[i] > 0 || nt[i] > 0) {
                cout<<-1<<'\n';
                return;
            }
        }
        cout<<1<<'\n';
        return;
    }
    debug(dep, ns, nt, base_s, base_t);
    if(base_s == 0 && base_t == 0) {
        cout<<-1<<'\n';
        return;
    }
    rep(i, 0, n) {
        if(dep[i] == 0) {
            if(ns[i] > 0 || nt[i] > 0) {
                cout<<-1<<'\n';
                return;
            }
        } else {
            assert(dep[i] > 0);
            if(base_t * dep[i] == nt[i]) {
                if(ns[i] != base_s*dep[i]) {
                    cout<<-1<<'\n';
                    return;
                }
                debug("colinear");
            } else {
                // ns[i]+nt[i]*ans==base_s*dep+base_t*dep*ans
                // ans = (base_s*dep-ns[i]) / (nt[i]-base_t*dep) 
                debug(ns[i],nt[i],base_s,base_t,dep[i]);
                int de = nt[i]-base_t*dep[i];
                int nu = base_s*dep[i]-ns[i];
                if(de < 0) {
                    nu *= -1, de *= -1;
                    if(nu <= 0) {
                        cout<<-1<<'\n';
                        return;
                    }
                }
                debug(nu, de, ans);
                if(nu % de != 0) {
                    cout<<-1<<'\n';
                    return;
                }
                int new_ans = nu / de;
                assert(new_ans > 0);
                if(ans == -1) {
                    ans = new_ans;
                } else {
                    if(ans != new_ans) {
                        cout<<-1<<'\n';
                        return;
                    }
                }
            }
        }
    }
    if(ans == -1) ans = 1;
    cout << ans << '\n';
}

// akt+kb==ct+d
signed main() {
    int T; T=1;
    while(T--) solve();
    return 0;
}