/*

  "With age, comes wisdom. With travel, comes understanding.
   Remember that happiness is a way of travel – not a destination"

*/

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define int            int
#define ld             long double
#define F              first
#define S              second
#define pb             push_back
#define si             set <int>
#define vi             vector <int>
#define pii            pair <int, int>
#define vpi            vector <pii>
#define vpp            vector <pair<int, pii>>
#define mii            map <int, int>
#define mpi            map <pii, int>
#define spi            set <pii>
#define endl           "\n"
#define sz(x)          ((int) x.size())
#define all(p)         p.begin(), p.end()
#define que_max        priority_queue <int>
#define que_min        priority_queue <int, vi, greater<int>>
#define bug(...)       __f (#__VA_ARGS__, __VA_ARGS__)
#define print(a)       for(auto x : a) cout << x << " "; cout << endl
#define print1(a)      for(auto x : a) cout << x.F << " " << x.S << endl
#define print2(a,x,y)  for(int i = x; i < y; i++) cout<< a[i]<< " "; cout << endl

inline int power(int a, int b)
{
     int x = 1;
     while (b)
     {
          if (b & 1) x *= a;
          a *= a;
          b >>= 1;
     }
     return x;
}

typedef tree<pii, null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update> Set;

template <typename Arg1>
void __f (const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << endl; }
template <typename Arg1, typename... Args>
void __f (const char* names, Arg1&& arg1, Args&&... args)
{
     const char* comma = strchr (names + 1, ',');
     cout.write (names, comma - names) << " : " << arg1 << " | "; __f (comma + 1, args...);
}

const int N = 25;
int a[N], n, m, k;
vpi v[N];

void solve()
{
     int i, j;
     cin >> n;

     for (i = 1; i <= n; i++)
     {
          cin >> m;
          for (j = 1; j <= m; j++)
          {
               int x, y; cin >> x >> y;
               v[i].pb({x, y});
          }
     }
     int mx = 0;
     for (i = 1; i < (1 << n); i++)
     {
          si st;
          for (j = 0; j < n; j++)
          {
               if (i & (1 << j))
                    st.insert(j + 1);
          }
          int ok = 1;
          // print(st);
          for (auto x : st)
          {
               // print1(v[x]);
               for (auto y : v[x])
               {
                    // bug(y.F, y.S);
                    if (st.find(y.F) == st.end())
                    {
                         // bug(y.S);
                         if (y.S == 1)
                         {
                              ok = 0;
                              break;
                         }
                    }
                    else
                    {
                         // bug(y.S);
                         if (y.S == 0)
                         {
                              ok = 0;
                              break;
                         }
                    }
               }
               // bug(ok);
               if (!ok)
                    break;
          }
          if (ok)
               mx = max(mx, sz(st));
     }
     cout << mx;

}

int32_t main()
{
     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
     cout << setprecision(9) << fixed;
     clock_t z = clock();
     solve();
     cerr << "Run Time : " << ((double)(clock() - z) / CLOCKS_PER_SEC);

     return 0;
}

Measured memory_bytes: 256