#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <iomanip>
#include <assert.h>
#include <array>
#include <cstdio>
#include <cstring>
#include <random>
#include <functional>
#include <numeric>
#include <bitset>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define minimize(a, x) a = std::min(a, x)
#define maximize(a, x) a = std::max(a, x)

using ll  = long long;
int const inf = 1<<29;

int main() {

  int n; cin >> n;
  set<int> st, ust;
  rep(i, n) {
    int a, b, c, d; cin >> a >> b >> c >> d;
    string s; cin >> s;
    if(s == "NO") {
      ust.insert(a);
      ust.insert(b);
      ust.insert(c);
      ust.insert(d);
    }
    else {
      st.insert(a);
      st.insert(b);
      st.insert(c);
      st.insert(d);
    }
  }

  int anss = -1;
  REP(i, 0, 10) {
    if(ust.count(i)) { continue; }
    if(st.count(i)) {
      cout << i << endl;
      exit(0);
    }
    else {
      anss = i;
    }
  }

  cout << anss << endl;

  return 0;
}