#include<bits/stdc++.h>
#include<algorithm>
#include<math.h>
#include<string>
#include<iostream>
#include<vector>
#include<cstdlib>
#include<stdio.h>
#include<cmath>
#include<limits>
#include<iomanip>

using namespace std;

const long long INF = 1LL << 60;

//各桁の和を出力
long long Sum(long long n) {
long long m=0;
  while(n){
    m+=n%10;
    n/=10;
  }
  return m;
}

const int MAX = 510000;
const int MOD = 1000000007;
 
long long fac[MAX], finv[MAX], inv[MAX];
 
void Comuse() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}


#define comuse Comuse()
//nCk(comuseを使え)
long long combi(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
//pCk(comuseを使え)
long long perm(int n,int k){
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] % MOD) % MOD;
}

//最小公倍数(aとbの)
long long lcm(long long a,long long b){
  long long n;
  n=a/__gcd(a,b)*b;
  return n;
}

//auto A = div(n)
vector<long long> div(long long n){
  vector<long long> ret;
  for(long long i=1;i*i<=n;i++){
    if(n%i==0){
      ret.push_back(i);
      if(i*i!=n){
        ret.push_back(n/i);
      }
    }
  }
  sort(ret.begin(),ret.end());
  return ret;
}

//(aのn乗をmodで割ったあまり)
long long modpow(long long a,long long n,long long mod){
  long long ans=1;
  while(n>0){
    if(n&1){
      ans=ans*a%mod;
    }

    a=a*a%mod;
    
    n>>=1;
  }

  return ans;
}

void Solve();


const int MAX_N = 131072;
//segment tree 
int NN;
int seg[MAX_N*2-1];
void seguse(){
  for(int i=0;i<2*NN-1;i++){
    seg[i]=INT_MAX;
  }
}

signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<setprecision(20)<<fixed;
  Solve();
}

///////////////////////////////////////////////////////////

int N;
int maxx = 0;

bool kensho(vector<int> shoujikikana, vector<vector<vector<int>>> &shougen, vector<int> &hito){
  for(int i = 0; i < N; i++){
    for(int j = 0; j < hito[i]; j++){
      if(shoujikikana[i] == 1 && shougen[i][j][1] != shoujikikana[shougen[i][j][0]-1]){
        return false;
      }
    }
  }
  //cout << "yes" <<endl;
  return true;
}

void erabu(int i, int n,vector<int> &shoujikikana, vector<vector<vector<int>>> &shougen, vector<int> &hito){
  if(i == n){
    int count = 0;
    for(int j = 0; j < n; j++){
      if(shoujikikana[j] == 1){
        count ++;
      }
    }
    if(kensho(shoujikikana, shougen, hito) && maxx < count){
      for(int k = 0; k < n; k++){
        //cout << shoujikikana[k] <<endl;
      }
    maxx = count;
    return;
    }
    return;
  }
  shoujikikana[i] = 0;
  erabu(i+1, n, shoujikikana, shougen, hito);

  shoujikikana[i] = 1;
  erabu(i+1, n, shoujikikana, shougen, hito);

  return;
}

void Solve(){
  cin >> N;
  vector<int> hito(N);
  vector<vector<vector<int>>> shougen(N, vector<vector<int>>(N, vector<int>(2)));
  for(int i = 0; i < N; i++){
    cin >> hito[i];
    for(int j = 0; j < hito[i]; j++){
      cin >> shougen[i][j][0] >> shougen[i][j][1];
    }
  }
  vector<int> shoujikikana(N);
  erabu(0,N, shoujikikana, shougen, hito);
  cout << maxx <<endl;
}


Measured memory_bytes: 256