#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
#define int ll
#define double long double
void YN(bool flg){cout<<(flg?"YES":"NO")<<endl;}
void Yn(bool flg){cout<<(flg?"Yes":"No")<<endl;}
void yn(bool flg){cout<<(flg?"yes":"no")<<endl;}
#define SORT(a) sort(a.begin(),a.end())
#define REVERSE(a) reverse(a.begin(),a.end())
#define REP(i, n) for(int i = 0; i < n; i++)
#define REPR(i, n) for(int i = n; i >= 0; i--)
#define FOR(i, m, n) for(int i = m; i < n; i++)
#define out(n) cout << n << endl;
typedef vector<int> VI;
typedef vector<VI> VVI;
const int MOD = 1000000007;
const long long INF = 10e10;
const double PI = acos(-1.0);
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T>auto MAX(const T& a) { return *max_element(a.begin(),a.end()); }
template<class T>auto MIN(const T& a) { return *min_element(a.begin(),a.end()); }
template<class T, class U>U SUM(const T& a, const U& v) { return accumulate(a.begin(),a.end(), v); }
template<class T, class U>int LOWER(const T& a, const U& v) { return lower_bound(a.begin(),a.end(), v) - a.begin(); }
template<class T, class U>int UPPER(const T& a, const U& v) { return upper_bound(a.begin(),a.end(), v) - a.begin(); }
int GCD(int a, int b) { return b ? GCD(b, a%b) : a; }
int LCM(int a, int b) { int g = GCD(a, b); return a / g * b; }
int POW(int a, int n) { int r = 1; while (n > 0) { if (n & 1)r *= a; a *= a; n /= 2; }return r; }
int isPrime(int n){if(n<2){return 0;}for(int i=2; i*i<=n; i++){if(n%i==0){return 0;}}return 1;}
/*素因数分解*/map< int64_t, int >prime_factor(int64_t n){map< int64_t, int > ret;for(int64_t i = 2; i * i <= n; i++) {while(n % i == 0) {ret[i]++;n /= i;}}if(n != 1) ret[n] = 1;return ret;}
/*約数列挙*/vector<int> getDivisor(int n){vector<int> v; for(int i=1; i*i<=n; i++){if(n%i==0){v.push_back(i);if(i!=n/i){v.push_back(n/i);}}}sort(v.begin(),v.end()); return v;}
//----------------ライブラリとか----------------

int N;
int A[20];
int x[20][20];
int y[20][20];

int counter(int x) {
    if(x == 0) return 0;
    return counter(x >> 1) + (x & 1);
}

void solve() {
    cin >> N;
    for(int i = 1; i <= N; i++) {
        cin >> A[i]; //i番目の人の証言の個数
        for(int j = 1; j <= A[i]; j++) {
            //x[i][j]:=i番目の人のj番目の証言が誰に向けてのものか
            //y[i][j]:=i番目の人のj番目の証言の内容
            cin >> x[i][j] >> y[i][j];
        }
    }
    int ans = 0;
    for(int bits = 1; bits < (1 << N); bits++) { //2^N
        bool ok = true;
        for(int i = 1; i <= N; i++) {
            if(!(bits & (1 << (i-1)))) continue; //bitでi-1番目のフラグが消えていたらcontinue(i人目が不親切なら確かめなくて良い)
            for(int j = 1; j <= A[i]; j++) { //証言を確かめる
                // ((bits >> (x[i][j]-1)) & 1) := bitにx[i][j]-1のフラグが立っているか
                //  y[i][j]は実際の証言の内容
                // 矛盾していたらtrueとなるのでokをfalseにする
                if(((bits >> (x[i][j]-1)) & 1) != y[i][j]) ok = false;
            }
        }
        //要はchmax
        if(ok) ans = max(ans, counter(bits));
    }
    cout << ans << endl;
    return;
}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout<<fixed<<setprecision(15);

    solve();

    return 0;
}

Measured memory_bytes: 256