#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

#define fi first
#define se second
#define mp make_pair
#define fastIO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

int main(){
    fastIO;
    freopen("in.txt", "r", stdin);
    int n;
    cin >> n;
    string s;
    vector<int> a(n), b(n), dep(n);
    int d = -1;
    for(int i = 0; i < n; i ++) {
        cin >> s;
        char l = s.back();
        s.pop_back();
        for(char x : s){
            if(x == 's') b[i] ++ ;
            else a[i] ++ ;
        }
        if(l == '{'){
            d ++ ;
            dep[i]=d;
        }
        else{
            dep[i]=d;
            d -- ;
        }
    }
    int r;
    for(int K = 1; K <= (int)1e5 + 10; K ++ ){
        r = -2;
        int cur;
        for(int i = 0 ; i < n; i ++) {
            if(K * dep[i] - b[i] >= 0){
                if(a[i] == 0){
                    if(K * dep[i] != b[i]){
                        r = -1;
                        break;
                    }
                }
                else{
                    cur = (K * dep[i] - b[i]) / a[i];
                    if(r != -2 && r != cur) r = -1;
                    else r = cur;
                }
            }
            else{
                r = -1;
                break;
            }
        }
        if(r != -1){
            r=max(r,1);
            cout << r << "\n";
            return 0;
        }
    }
    cout << "-1\n";
    return 0;
}