#include <bits/stdc++.h>
#include <math.h>
//in the name of god,aka allah
//**gray sety orz**
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-fdelete-null-pointer-checks")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#pragma GCC optimize("unroll-loops")
using namespace std;
#define pi pair<long long , long long>
#define pii pair<long long , pair<long long , long long>>
const int maxm = 5e5;
const long long mod = 1e9 + 7 ;
typedef long long ll;
ll l,r,mid;
ll n,m;
ll dis[maxm] , sum[maxm];
bool isval(int mid){
//cout << mid <<" " << mid*mid-mid <<endl;
if (((mid-1)*mid)/2 < m) return 0;
return 1;
}
ll darage[maxm] , ss , mm;
queue<int> q;
vector<pi> g[maxm] , z[maxm];
ll sath[maxm];
bool vis[maxm] , gos[maxm];
ll pedaret[maxm];
ll get_par(ll v){
if (pedaret[v]==v) return v;
return pedaret[v] = get_par(pedaret[v]);
}
void merge(ll r , ll q){
if (get_par(r)!=get_par(q))l+=max(darage[r],darage[q])*1ll*sath[r]*1ll*sath[q];
r = get_par(r) , q = get_par(q);
if (r!=q){
if (sath[r]<sath[q]) swap(r,q);
pedaret[q] = r;
sath[r] += sath[q];
}
return ;
}
ll pars1[maxm] , pars2[maxm];
vector<ll> se[maxm];
set<pi> st;
ll rp[maxm];
pi w[maxm];
ll dp[maxm];
//ll rw[maxm][maxm];
map<ll,ll> mp;
int main(){
ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
cin >>n;
for (int i=0; i<n; i++) cin>>w[i].first>>w[i].second;
sort(w,w+n);
for (int mask=0; mask<(1<<n); mask++){
vector<pi> A,B;
for (int i=0; i<n; i++){
if (mask&(1<<i)) A.push_back(w[i]);
else B.push_back(w[i]);
}
l = 0;
for (int i=0; i<A.size(); i++){
for (int j=i+1; j<A.size(); j++){
//cout<<A[i].first<<" "<<A[i].second<<" "<<A[j].first<<" "<<A[j].second<<endl;
if (A[i].first<=A[j].first && A[i].second<=A[j].second && A[j].first<=A[i].second) l = 1;
}
}
for (int i=0; i<B.size(); i++){
for (int j=i+1; j<B.size(); j++){
//cout<<B[i].first<<" "<<B[i].second<<" "<<B[j].first<<" "<<B[j].second<<endl;
if (B[i].first<=B[j].first && B[i].second<=B[j].second && B[j].first<=B[i].second) l = 1;
}
}
//if (!l) cout<<mask<<endl;
mid+=(1-l);
}
cout<<mid<<'\n';
}
