#define STOPIT
#include <bits/stdc++.h>
#define loop(n) for (int ngtkana_is_a_genius = 0; ngtkana_is_a_genius < int(n); ngtkana_is_a_genius++)
#define rep(i, begin, end) for (int i = int(begin); (i) < int(end); i++)
#define all(v) v.begin(), v.end()
#define rand(l, r) std::uniform_int_distribution<>(l, r)(mt)
using lint = long long;
auto mt = std::mt19937_64(std::random_device{}());
auto cmn = [](auto& a, auto b){ if (a > b) {a = b; return true;} return false; };
auto cmx = [](auto& a, auto b){ if (a < b) {a = b; return true;} return false; };
void debug_impl() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_impl(Head head, Tail... tail) { std::cerr << " " << head; debug_impl(tail...); }
#ifndef STOPIT
#define debug(...)\
  do {\
    std::cerr << std::boolalpha << "[" << #__VA_ARGS__ << "]:";\
    debug_impl(__VA_ARGS__);\
    std::cerr << std::noboolalpha;\
  } while (false)
#else
#define debug(...) {}
#endif

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr>
std::istream& operator>> (std::istream& is, Container& v)
  { for (auto & x : v) { is >> x; } return is; }

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr >
std::ostream& operator<< (std::ostream& os, Container const& v) {
 os << "{";
  for (auto it = v.begin(); it != v.end(); it++)
    {os << (it != v.begin() ? "," : "") << *it;}
  return os << "}";
}

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& tuple_input_impl(std::istream& os, Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
  { (void)std::initializer_list<int>{((void)(os >> std::get< Inds >(tuple)), 0)...}; return os; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& operator>> (std::istream& os, Tuple<Args...>& tuple)
  { return tuple_input_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& tuple_output_impl(std::ostream& os, const Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
  { os << "("; (void)std::initializer_list<int>{((void)(os << (Inds > 0 ? "," : "") << std::get< Inds >(tuple)), 0)...}; return os << ")"; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& operator<< (std::ostream& os, const Tuple<Args...>& tuple)
 { return tuple_output_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < class Value >
bool bat(Value x, std::size_t pos) { return (x >> pos) & Value{1}; }

int main() {
  std::cin.tie(0); std::cin.sync_with_stdio(false);
  int n; std::cin >> n;
  std::vector<std::vector<std::pair<int,int>>> z(n);
  rep(i,0,n) {
    int k; std::cin >> k;
    loop(k) {
      int x, y; std::cin >> x >> y;
      x--;
      z.at(i).emplace_back(x,y);
    }
  }
  debug(z);

  int N = 1<<n;
  int ans = 0;
  rep(bs,0,N) {
    debug(bs);
    bool ng = false;
    rep(i,0,n) {
      if (!bat(bs,i)) continue;
      for (auto&& pair : z.at(i)) {
        int j,c; std::tie(j,c) = pair;
        if (c != bat(bs,j)) {
          debug(i,j,c,bat(bs,j));
          ng = true;
          break;
        }
      }
      if (ng) break;
    }
    if (!ng) {
      cmx(ans, __builtin_popcount(bs));
    }
  }
  std::cout << ans << std::endl;
  return 0;
}

Measured memory_bytes: 256