#include <bits/stdc++.h>
#define fi first
#define se second
#define int long long
using namespace std;
using ll = long long;
using ii = pair<int,int>;
using pii = pair<int,ii>;
using aa = array<int,4>;
const int N = 1e5+5;
const int INF = 1e9;
const int MOD = 1e9+7;
int n,ans,dp[N];
aa p[N];
vector <int> compress;
struct SMT{
int n;
vector<int> t;
vector<int> lazy;
SMT(int _n = 0) : n(_n){
t.assign((n << 2),0);
lazy.assign((n << 2),0);
}
void push(int id,int l,int r){
if (l == r || !lazy[id]) return;
for (int i = 0; i <= 1; i++){
t[id*2+i] += lazy[id];
lazy[id*2+i] += lazy[id];
}
lazy[id] = 0;
}
void update(int id,int l,int r,int u,int v){
}
};
int calc(int val){
return lower_bound(compress.begin(),compress.end(),val) - compress.begin();
}
/*
p[i][0]: l
p[i][1]: r
p[i][2]: l1
p[i][3]: r1
*/
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
cin >> n;
for (int i = 1; i <= n; i++){
for (int j = 0; j <= 3; j++){
cin >> p[i][j];
compress.push_back(p[i][j]);
}
}
sort(p+1,p+1+n);
sort(compress.begin(),compress.end());
compress.erase(unique(compress.begin(),compress.end()),compress.end());
dp[1] = 1;
for (int i = 2; i <= n; i++){
for (int j = i - 1; j >= 1; j--){
if (p[j][1] <= p[i][0] && p[j][3] <= p[i][2]){
dp[i] = max(dp[i],dp[j] + 1);
}
}
ans = max(ans,dp[i]);
}
cout << ans;
return 0;
}
