#include <iostream>
#include <string>
using namespace std;
int n, num[10], a[4];
string s;

int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    for (auto& e : a)  cin >> e;
    cin >> s;
    if (s == "NO") {
      for (auto& e : a) num[e]++;
    } else {
      for (auto& e : num) e++;
      for (auto& e : a) num[e]--;
    }
  }
  int ans = -1;
  for (int i = 0; i <= 9; i++) {
    if (num[i] == 0) {
      ans = i;
      break;
    }
  }
  cout << ans << endl;
}