#include <iostream>
#include <iomanip>
#include <string>
#include <stack>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <iterator>
#include <map>
#include <set>
#include <queue>
#include <list>
#include <regex>
using namespace std;
using pii  = pair<int,int>;
using ll=long long;
using ld=long double;
#define pb push_back
#define mp make_pair
#define sc second
#define fr first
#define stpr setprecision
#define cYES cout<<"YES"<<endl
#define cNO cout<<"NO"<<endl
#define cYes cout<<"Yes"<<endl
#define cNo cout<<"No"<<endl
#define rep(i,n) for(ll i=0;i<(n);++i)
#define Rep(i,a,b) for(ll i=(a);i<(b);++i)
#define rrep(i,n) for(int i=n-1;i>=0;i--)
#define rRep(i,a,b) for(int i=a;i>=b;i--)
#define crep(i) for(char i='a';i<='z';++i)
#define psortsecond(A,N) sort(A,A+N,[](const pii &a, const pii &b){return a.second<b.second;});
#define ALL(x) (x).begin(),(x).end()
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define endl '\n'
int ctoi(const char c){
  if('0' <= c && c <= '9') return (c-'0');
  return -1;
}
ll gcd(ll a,ll b){return (b == 0 ? a : gcd(b, a%b));}
ll lcm(ll a,ll b){return a*b/gcd(a,b);}
constexpr ll MOD=1000000007;
constexpr ll INF=1000000011;
constexpr ll MOD2=998244353;
constexpr ll LINF = 1001002003004005006ll;
constexpr ld EPS=10e-8;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> istream& operator>>(istream& is,vector<T>& v){for(auto&& x:v)is >> x;return is;}
template<typename T,typename U> istream& operator>>(istream& is, pair<T,U>& p){ is >> p.first; is >> p.second; return is;}
template<typename T,typename U> ostream& operator>>(ostream& os, const pair<T,U>& p){ os << p.first << ' ' << p.second; return os;}
template<class T> ostream& operator<<(ostream& os, vector<T>& v){
  for(auto i=begin(v); i != end(v); ++i){
    if(i !=begin(v)) os << ' ';
    os << *i;
  }
  return os;
}

ll ma = 0;
ll N,A[20],x,y;
ll D[20];
vector<vector<pair<ll,ll>>> V(20);

int main(){
    ll C[20];
    cin >> N ;
    rep(i,N){
        ll A;
        cin >> A;
        rep(j,A){
            cin >> x >> y;
            V[i].pb(mp(x-1,y));
        }
    }
    ll ans =0;
    rep (bit,1<<N) {  // 0~2^N-1 までのbit 全探索
        ll T,M;
        rep(i,20){
            C[i]=2;
        }
        T=0;M=0;
        rep (i, N){
            if (bit & (1<<i)) { // i が bit に入るかどうか
                M++;
                if(C[i]==0 || T==1){
                    T=1;
                    break;
                }
                C[i]=1;
                rep(j,V[i].size()){
                    if(C[V[i][j].fr] != 2 && C[V[i][j].fr]!= V[i][j].sc){
                        T=1;
                        break;
                    }
                    C[V[i][j].fr]= V[i][j].sc;
                }
            }
            else{
                if(C[i]==1){
                    T=1;
                    break;
                }
                C[i]=0;
            }
        }
        if(T==0){
            ans = max(ans,M);
        }
    } 
    cout << ans  << endl;
}

Measured memory_bytes: 256