#include<bits/stdc++.h>
using namespace std;
#define int long long

const int M = 100006;
const int N = 106;

string grid[N];
int level[N],scount[N],tcount[N];
signed main(){
    int n;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>grid[i];
    }
    int lvl = 0;
    for(int i=0;i<n;i++){
        int s,t;
        for(int j=0;j<grid[i].size();j++){

            if( grid[i][j] == 's' ) scount[i]++;
            if( grid[i][j] == 't' ) tcount[i]++;
            if( grid[i][j] == '{' ) {
                level[i] = lvl;
                lvl++;
            }
            if( grid[i][j] == '}' ) {
                lvl--;
                level[i] = lvl;
            }
        }
        //cout<<level[i]<<endl;
    }
    for(int i=0;i<n;i++){
        if( level[i] == 0 and (tcount[i]+scount[i]) ){
            cout<<-1<<endl;
            return 0;
        }
    }
    for(int i=1;i<N;i++){
        int k = -1;
        bool pos = true;
        for(int j=0;j<n;j++){
            if( level[j] == 0 ) continue;
            int len = tcount[j]*i + scount[j]; 
            if( len%level[j] != 0 ) {
                pos = false;
                break;
            }
            int temp = len/level[j];
           // cout<<level[j]<<" "<<len<<" "<<temp<<endl;
            if( temp != i ) pos = false;
        }

        if( pos ){
            cout<<i<<endl;
            return 0;
        }
    }
    cout<<-1<<endl;
}

/*
10
{
ss{
sts{
tt}
t}
t{
ss}
}
{
}
*/