#pragma GCC optimize(3,"Ofast","inline")
#include<iostream>
#include<string>
#include<algorithm>
#include<queue>
#include<map>
#include<ctime>
using namespace std;
#define ll long long
const int N=5005;
const ll mod=998244353;
ll qpow(ll a,ll b){
	ll ans=1;
	if(b==0)
	return 1;
	if(b%2)
	ans=a;
	ll t=qpow(a,b/2);
	return t*t%mod*ans%mod;
}
ll inv(ll a){
	return qpow(a,mod-2);
}
int dp[N][N];
int dq[N][N];
struct pt{
	int l1;
	int r1;
	int l2;
	int r2;
};
pt a[N];
void ins(int i,int x,int y){
	dp[i][x]=max(dp[i][x],y);
	dq[i][y]=max(dq[i][y],x);
}
void solve(){
	ll n;
	cin>>n;
	for(int i=1;i<=n;i++){
		int x,y,z,h;
		cin>>x>>y>>z>>h;
		a[i]={x,y,z,h};
	}
	for(int i=0;i<=n;i++){
		for(int j=0;j<=n;j++){
			dp[i][j]=dq[i][j]=-n-1;
		}
	}
	dp[0][0]=0;
	for(int i=1;i<=n;i++){
		for(int j=0;j<=n;j++){
			int x=j,y=dp[i-1][j];
			if(x>=a[i].l1&&x<=a[i].r1&&y>=a[i].l2&&y<=a[i].r2){
				ins(i,x+1,y);
				ins(i,x,y+1);
			}
			ins(i,x,y);
		}
		for(int j=0;j<=n;j++){
			int y=j,x=dq[i-1][j];
			if(x>=a[i].l1&&x<=a[i].r1&&y>=a[i].l2&&y<=a[i].r2){
				ins(i,x+1,y);
				ins(i,x,y+1);	
			}
			ins(i,x,y);
		}
	}
	int ans=0;
	for(int j=0;j<=n;j++){
		ans=max(ans,dp[n][j]+j);
		ans=max(ans,dq[n][j]+j);
	}
	cout<<ans<<'\n';
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0); 

	solve();
}