#include <bits/stdc++.h>
#define boost_io ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define rep(i,a,b) for(int i=a;i<b;i++)
#define num(a) a-'0'
#define maxself(a,b) if(b>a)a=b
#define minself(a,b) if(b<a)a=b;
#define debug(x) cout<<#x<<":"<<x<<" "
#define all(a) (a).begin(), (a).end()
#define vi vector<int>
#define vl vector<long long int>
#define v vector
#define p pair
#define pb push_back
#define mk make_pair
#define f first
#define s second
#define ln "\n"	
typedef long long int ll;
typedef long double ld;
typedef double d;
using namespace std;
ll modF=1e9+7;
ll INF=1e11;

void solve(){
	int n;
	cin>>n;
	v<v<p<int,int>>> a(n);
	int h;
	rep(i,0,n){
		cin>>h;
		rep(j,0,h){
			int x,pos;
			cin>>x>>pos;
			a[i].pb(mk(x,pos));
		}
	}
	ll ans=0;
	for(int bit=0;bit<(1<<n);bit++){
		int counter=0;
		int pos=1;
		for(int j=0;j<n;j++){
			if(1<<j & bit){
				for(auto e:a[j]){
					h=((1<<(e.f-1)) & bit);
					if(h==0 && e.s==1){
						pos=0;
					}
					else if(h!=0 && e.s==0){
						pos=0;
						break;
					}
				}
				counter++;
			}
		}
		if(pos){
			maxself(ans,counter);
		}
	}
	cout<<ans<<ln;
}

int main(){
	boost_io;
	solve();
	return 0;
}
/*

                   _ooOoo_
                  o8888888o
                  88" . "88
                  (| -_- |)
                  O\  =  /O
               ____/`---'\____
             .'  \\|     |//  `.
            /  \\|||  :  |||//  \
           /  _||||| -:- |||||-  \
           |   | \\\  -  /// |   |
           | \_|  ''\---/''  |   |
           \  .-\__  `-`  ___/-. /
         ___`. .'  /--.--\  `. . __
      ."" '<  `.___\_<|>_/___.'  >'"".
     | | :  `- \`.;`\ _ /`;.`/ - ` : | |
     \  \ `-.   \_ __\ /__ _/   .-` /  /
======`-.____`-.___\_____/___.-`____.-'======
                   `=---='
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                    prayer
*/

// g++ -std=c++11 a.cpp
#include<iostream>
#include<vector>
#include<string>
#include<algorithm>	
#include<map>
#include<set>
#include<unordered_map>
#include<utility>
#include<cmath>
#include<random>
#include<cstring>
#include<queue>
#include<stack>
#include<bitset>
#include<cstdio>
#include<sstream>
#include<iomanip>
#include<assert.h>
#include<typeinfo>
#define loop(i,a,b) for(long long i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define FOR(i,a) for(auto i:a)
#define pb push_back
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)
#define show1d(v) rep(_,v.size())cout<<" "<<v[_];cout<<endl;
#define show2d(v) rep(__,v.size()){rep(_,v[__].size())cout<<" "<<v[__][_];cout<<endl;}
using namespace std;
//kaewasuretyuui
typedef long long ll;
#define int ll
typedef int Def;
typedef pair<Def,Def> pii;
typedef vector<Def> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef pair<Def,pii> pip;
typedef vector<pip>vip;
// #define mt make_tuple
// typedef tuple<int,int,int> tp;
// typedef vector<tp> vt;
template<typename A,typename B>bool cmin(A &a,const B &b){return a>b?(a=b,true):false;}
template<typename A,typename B>bool cmax(A &a,const B &b){return a<b?(a=b,true):false;}
//template<class C>constexpr int size(const C &c){return (int)c.size();}
//template<class T,size_t N> constexpr int size(const T (&xs)[N])noexcept{return (int)N;}
const double PI=acos(-1);
const double EPS=1e-9;
Def inf = sizeof(Def) == sizeof(long long) ? 2e18 : 1e9+10;
int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};

signed main(){
	int n;
	cin>>n;
	vvi in(n,vi(2));
	rep(i,n)rep(j,2)cin>>in[i][j];
	sort(all(in),[](vi a,vi b){
		return a[0]+a[1]<b[0]+b[1];
	});
	vi dp(n+1,inf);
	dp[0]=0;
	rep(i,n){
		vi ndp=dp;
		rep(j,n){
			if(dp[j]<=in[i][0])
				cmin(ndp[j+1],dp[j]+in[i][1]);
		}
		dp=ndp;
	}
	int out=inf;
	rep(i,n+1)if(dp[i]-inf)out=i;
	cout<<out<<endl;
}














