#include <bits/stdc++.h>
#define pb push_back
#define fs first
#define sc second
#define rep(i, j, k) for(int i = j; i <= k; ++ i)
#define per(i, j, k) for(int i = j; i >= k; -- i)
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int N = 110;
int n, a[N], b[N], c[N];
int det(int a, int b, int c, int d) { //[a b][c d]
  return a * d - b * c;
}
void check(int x, int y) {
  if(x >= 1 && y >= 1) {
    rep(i, 1, n) if(a[i] * x + b[i] * y != c[i]) return ;
    printf("%d\n", x);
    exit(0);
  }
}
int main() {
  scanf("%d", &n);
  static char s[1024];
  int o = 0, u = 0, v = 0;
  rep(i, 1, n) {
    scanf("%s", s);
    int m = strlen(s);
    int tab = 0, space = 0;
    for(int j = 0; j < m - 1; j ++) {
      tab += s[j] == 't';
      space += s[j] == 's';

      //tab = x, indent = y
      //tab*x + (- o) y = - space
      //ax + by = c
      
    }
    o -= (s[m-1] == '}');

    a[i] = tab;
    b[i] = -o;
    c[i] = -space;
    if(o == 1) {
      if(!tab && !space) {
        puts("-1");
        exit(0);
      }
      u = tab;
      v = space;
    }

    o += (s[m-1] == '{');
  }
  rep(i, 1, n) rep(j, i + 1, n) if(det(a[i], b[i], a[j], b[j]) != 0) {
    int d = det(a[i], b[i], a[j], b[j]);
    int x = det(c[i], b[i], c[j], b[j]);
    int y = det(a[i], c[i], a[j], c[j]);
    if(x % d || y % d) {
      puts("-1");
      exit(0);
    }
    x /= d; y /= d;
    check(x, y);
    puts("-1");
    exit(0);
  }
  if(!u && !v) { //{}
    puts("1");
    exit(0);
  }
  int x, y;
  check(1, u + v);
  puts("-1");
  exit(0);
  return 0;
}
/*
2
{
}

4
{
tt{
sssst}
}
*/