import java.io.*;
import java.io.IOException;
import java.util.*;

@SuppressWarnings({"rawtypes", "unchecked"})
class Main {
    final static int INF = 1 << 28;
    final static long LNF = 1L << 60;
    final static double EPS = 1e-9;
    final static double GOLDEN_RATIO = (1.0 + Math.sqrt(5)) / 2.0;

    static final long MOD = 1_000_000_007;

    public static void main(String[] args) throws Exception {
        final MyScanner sc = new MyScanner();
        // Failed to predict input format
        int N = sc.nextInt();
        int[] honest = new int[N];
        int[] unkind = new int[N];

        for (int i = 0; i < N; i++) {
            int A = sc.nextInt();
            for (int j = 0; j < A; j++) {
                int x = sc.nextInt() - 1;
                int y = sc.nextInt();
                if(y == 1) honest[i] |= 1 << x;
                else unkind[i] |= 1 << x;
            }
        }

        int ans = 0;
        for (int i = 0; i < 1 << N; i++) {
            boolean flag = true;
            for (int j = 0; j < N; j++) {
                if((i >> j & 1) == 1) {
                    if((i & honest[j]) != honest[j]) flag = false;
                    if((~i & unkind[j]) != unkind[j]) flag = false;
                }
            }
            if(flag && ans < Integer.bitCount(i)) 
                ans = Integer.bitCount(i);
        }
        System.out.println(ans);
    }



    static class MyScanner {
 
        BufferedReader br;
        StringTokenizer st;
 
        MyScanner(FileReader fileReader) {
            br = new BufferedReader(fileReader);
        }
 
        MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
 
        String nn() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        String next() {
            String ans = "";
            try {
                ans = br.readLine();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            return ans;
        }
 
        char nextChar() {
            return nn().charAt(0);
        }
 
        int nextInt() {
            return Integer.parseInt(nn());
        }
 
        long nextLong() {
            return Long.parseLong(nn());
        }
 
        double nextDouble() {
            return Double.parseDouble(nn());
        }
 
        Integer[] niArr0(int n) {
            Integer[] ar = new Integer[n];
            for (int i = 0; i < n; i++) {
                ar[i] = nextInt();
            }
            return ar;
        }
 
        Integer[] niArr1(int n) {
            Integer[] ar = new Integer[n + 1];
            for (int i = 1; i <= n; i++) {
                ar[i] = nextInt();
            }
            return ar;
        }
 
        Long[] nlArr0(int n) {
            Long[] ar = new Long[n];
            for (int i = 0; i < n; i++) {
                ar[i] = nextLong();
            }
            return ar;
        }
 
        Long[] nlArr1(int n) {
            Long[] ar = new Long[n + 1];
            for (int i = 1; i <= n; i++) {
                ar[i] = nextLong();
            }
            return ar;
        }
    }

}


Measured memory_bytes: 21588