#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("Ofast,unroll-loops")
#define pii pair<int,int>
using namespace __gnu_pbds;
using namespace std;
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define int long long
#define f first
#define s second
#define pii pair<int,int>
template<class T>bool umax(T &a,T b){if(a<b){a=b;return true;}return false;}
template<class T>bool umin(T &a,T b){if(b<a){a=b;return true;}return false;}
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
tree_order_statistics_node_update> ordered_set;
const int mod= 1e9 +7;
const int N=1e5*4;
int binpow (int a, int n) {
if (n == 0)
return 1;
if (n % 2 == 1)
return binpow (a, n-1) * a;
else {
int b = binpow (a, n/2);
return b * b;
}
}
void solve(){
int n,m,k;
cin>>n;
vector<pair<int,pii>>v;
for(int i = 0;i<n;i++){
int l,r;
cin>>l>>r;
v.pb({l,{1,i}});
v.pb({r,{2,i}});
}
sort(all(v));
int ans = 0;
vector<int>vis(n);
for(int mask = 0;mask<(1<<n);mask++){
deque<int>q1,q2;
bool flag = true;
int cnt = 0,cont = 0;
for(int i = 0;i<n*2;i++){
if(v[i].s.f==1){
if(((mask>>cnt)&1)==1){
q2.push_back({v[i].s.s});
vis[v[i].s.s] = 2;
}
if(((mask>>cnt)&1)==0){
q1.push_back({v[i].s.s});
vis[v[i].s.s] = 1;
}
cnt++;
}
else{
if(vis[v[i].s.s]==1){
if(q1.back()!=v[i].s.s){
flag = false;
break;
}
q1.pop_back();
}
else{
if(q2.back()!=v[i].s.s){
flag = false;
break;
}
q2.pop_back();
}
}
}
if(flag)ans++;
}
cout<<ans<<"\n";
}
signed main()
{
// freopen("seq.in", "r", stdin);
// freopen("seq.out", "w", stdout);
ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
int cnt=0;
int tt=1;//cin>>tt;
while(tt--)solve();
}
