#pragma region header
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define rev(i, n) for(int i = (int)(n - 1); i >= 0; i--)
#define rev1(i, n) for(int i = (int)(n); i > 0; i--)
#define pb push_back
#define all(v) (v).begin(), (v).end()
#define resort(v) sort((v).rbegin(), (v).rend())
#define vi vector<int>
#define vvi vector<vector<int>>
#define vc vector<char>
#define vvc vector<vector<char>>
#define vb vector<bool>
#define vvb vector<vector<bool>>
using ll = long long;
using P = pair<int, int>;
/* ----------------よく使う数字や配列----------------- */
int dx[] = {1,0,-1,0};
int dy[] = {0,1,0,-1};
constexpr ll mod = 1e9+7;
constexpr ll inf = INT32_MAX/2;
constexpr ll INF = LLONG_MAX/2;
constexpr long double eps = DBL_EPSILON;
constexpr long double pi = 3.141592653589793238462643383279;
/* ----------------------end----------------------- */

/* --------------------テンプレート------------------ */
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
/* ----------------------end----------------------- */

/* --------------------ライブラリ-------------------- */
ll fact(int i) {       //階乗
    if (i == 0) return 1;
    return (fact(i - 1)) * i % mod;
}
ll gcd(ll a, ll b) {        //最大公約数
    if(b == 0) return a;
    return gcd(b, a % b); 
}
ll lcm(ll a, ll b) {      //最小公倍数
    return a * b / gcd(a, b);
}
int keta(ll n) {        //桁数を求める
    if(n == 0) return 1;
    int count = 0;
    while(n != 0) {
        n /= 10;
        count++;
    }
    return count;
}
ll ketasum(ll n) {    //各桁の和
    ll sum = 0;
    while(n != 0) {
        sum += n % 10;
        n /= 10;
    }
    return sum;
}
/* ----------------------end----------------------- */
#pragma endregion
signed main() { 
    int n;cin >> n;
    vvi w(n,vi(2,0));
    vector<pair<int,vvi>> v(n);
    rep(i, n) {
        int a;cin >> a;
        v[i].first=a;
        v[i].second=w;
        rep(j, a) {
            int x,y;cin >> x >> y;
            x--;
            v[i].second[j][0]=x,v[i].second[j][1]=y;
        }
    }
    vi ans(n,0);//0は不確定、1は親切確定、2は不親切確定
    int ma = -1;
    int count = 0;
    bool ok = true;
    rep(bit,(1<<n)) {
        ok=true;
        count=0;
        rep(i, n) {
            if((bit>>i)&1) ans[i]=2;
            else ans[i]=1,count++;
        }
        // cout << count << endl;
        rep(i, n) {
            if(ans[i]==2)continue;
            rep(j, v[i].first) {
                if(v[i].second[j][1]==0) {
                    if(ans[v[i].second[j][0]]==1) {
                        ok = false;
                        break;
                    }
                    // ans[v[i].second[j][0]]=2;
                }
                else {
                    if(ans[v[i].second[j][0]]==2) {
                        ok = false;
                        break;
                    }
                    // ans[v[i].second[j][0]]=1;
                }
            }
        }
        if(ok)chmax(ma,count);
    }
    cout << ma << endl;
    return 0;
}

Measured memory_bytes: 3628