#include<bits/stdc++.h>
using namespace std;
#define int long long
//shouldn't need, just in case...
int eve[2000005];
list<list<int> > luol;
list<int> tmp;
bool mk[1000005];
int par[1000005],sz[1000005];
int getr(int x){
if(par[x]==-1)return x;
int t=getr(par[x]);
if(mk[par[x]])mk[x]=!mk[x];
return par[x]=t;
}
bool bruh=false;
int c,d;
void merge(int a,int b){
//cout<<"MERGE"<<a<<' '<<b<<'\n';
c=getr(a);d=getr(b);
if(c==d){
//cout<<"path1\n";
//cout<<a<<' '<<b<<' '<<mk[a]<<mk[b]<<'\n';
if(mk[a]==mk[b])bruh=true;
return;
}
if(sz[c]<sz[d]){swap(c,d);swap(a,b);}
par[d]=c;
if(mk[a]==mk[b])mk[d]=true;//roots don't have marks so...
sz[c]+=sz[d];
}
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie(0);
int n;
cin>>n;
int a,b;
for(int i=0;i<n;i++){
cin>>a>>b;
eve[a]=(i+1);
eve[b]=-(i+1);
par[i+1]=-1;sz[i+1]=i;
}
for(int i=1;i<=(n*2);i++){
if(eve[i]>0){
luol.push_back(*(new list<int>));
luol.back().push_back(eve[i]);
}else{
eve[i]=-eve[i];
tmp.clear();
while(true){
if(luol.size()==0){
//cout<<"path 2\n";
goto hell;
}
if(luol.back().back()==eve[i]){
luol.back().pop_back();
if(luol.back().size()==0)luol.pop_back();
break;
}
merge(eve[i],luol.back().back());
if(bruh)goto hell;
tmp.splice(tmp.begin(),luol.back());
luol.pop_back();
}
if(tmp.size()>0){
luol.push_back(*(new list<int>));
luol.back().splice(luol.back().begin(),tmp);
}
}
/*for(auto x:luol){
for(auto y:x)cout<<y<<' ';cout<<'\t';
}cout<<'\n';*/
}
if(false){
hell:;
cout<<"0";
return 0;
}
int ans=1;
for(int i=1;i<=n;i++){
if(par[i]==-1){
ans*=2;
ans%=1000000007;
}
}
cout<<ans;
return 0;
}
