This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ii pair<int,int>
#define fi first
#define se second
#define endl '\n'
#define puf push_front
#define pof pop_front
#define pub push_back
#define pob pop_back
#define lb lower_bound
#define ub upper_bound
#define rep(x,s,e) for (auto x=s-(s>e);x!=e-(s>e);s<e?x++:x--)
#define all(x) (x).begin(),(x).end()
#define sz(x) (int) (x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD=1000000007;
int n;
ii arr[1000005];
vector<int> stk;
bool vis[1000005];
bool col[1000005];
struct node{
	int s,e,m;
	int cap=1;
	int idx=0;
	ii *arr=new ii[1];
	node *l,*r;
	
	node (int _s,int _e){
		s=_s,e=_e,m=s+e>>1;
		
		if (s!=e){
			l=new node(s,m);
			r=new node(m+1,e);
		}
	}
	
	void update(int i,ii k){
		if (idx==cap){
			//cerr<<"debug: "<<s<<" "<<e<<" "<<cap<<endl;
			
			ii *temp=new ii[cap*2];
			copy(arr,arr+cap,temp);
			arr=temp;
			cap*=2;
		}
		arr[idx++]=k;
		
		if (s==e) return;
		if (i<=m) l->update(i,k);
		else r->update(i,k);
	}
	
	ii query(int i,int j){
		if (s==i && e==j){
			while (idx && vis[arr[idx-1].se]) idx-=1;
			if (idx) return arr[idx-1];
			else return ii(-1e9,-1e9);
		}
		else if (j<=m) return l->query(i,j);
		else if (m<i) return r->query(i,j);
		else return max(l->query(i,m),r->query(m+1,j));
	}
} *root=new node(0,2000005), *root2=new node(0,2000005);
struct node2{
	int arr[4000010];
	
	const int BUF=2000005;
	
	node2(){
		memset(arr,-1,sizeof(arr));
	}
	
	void update(int i,int k){
		i+=BUF;
		
		while (i){
			arr[i]=max(arr[i],k);
			i>>=1;
		}
	}
	
	int query(int i,int j){
		i+=BUF,j+=BUF+1;
		int res=-1;
		
		for (;i<j;i>>=1,j>>=1){
			if (i&1){
				res=max(res,arr[i]);
				i++;
			}
			if (j&1){
				j--;
				res=max(res,arr[j]);
			}
		}
		
		return res;
	}
} *white=new node2(),*black=new node2();
int ans=1;
int main(){
	cin.tie(0);
	cout.tie(0);
	cin.sync_with_stdio(false);
	
	cin>>n;
	
	rep(x,0,n) cin>>arr[x].fi>>arr[x].se;
	
	vector<int> proc;
	rep(x,0,n) proc.pub(x);
	
	sort(all(proc),[](int i,int j){
		return arr[i].se<arr[j].se;
	});
	for (auto &it:proc) root->update(arr[it].fi,ii(arr[it].se,it));
	sort(all(proc),[](int i,int j){
		return arr[i].fi>arr[j].fi;
	});
	for (auto &it:proc) root2->update(arr[it].se,ii(-arr[it].fi,it));
	
	rep(x,0,n) if (!vis[x]){
		vis[x]=true;
		stk.pub(x);
		
		ans=2*ans%MOD;
		
		while (!stk.empty()){
			int pos=stk.back();
			stk.pob();
			
			//cout<<pos<<" "<<col[pos]<<endl;
			
			if (!col[pos]){
				white->update(arr[pos].fi,arr[pos].se);
			}
			else{
				black->update(arr[pos].fi,arr[pos].se);
			}
			
			while (true){
				int it=root->query(arr[pos].fi,arr[pos].se).se;
				if (it==-1e9 || arr[it].se<arr[pos].se) break;
				
				vis[it]=true;
				stk.pub(it);
				
				col[it]=!col[pos];
			}
			
			while (true){
				int it=root2->query(arr[pos].fi,arr[pos].se).se;
				if (it==-1e9 || arr[it].fi>arr[pos].fi) break;
				
				vis[it]=true;
				stk.pub(it);
				
				col[it]=!col[pos];
			}
		}
	}
	
	rep(x,0,n){
		if (!col[x]){ //white
			if (white->query(arr[x].fi,arr[x].se)>arr[x].se) ans=0;
		}
		else{ //black
			if (black->query(arr[x].fi,arr[x].se)>arr[x].se) ans=0;
		}
	}
	
	cout<<ans<<endl;
}
Compilation message (stderr)
port_facility.cpp: In constructor 'node::node(int, int)':
port_facility.cpp:40:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   40 |   s=_s,e=_e,m=s+e>>1;
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