/* in the name of allah */
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define F first
#define S second
#define mk make_pair
const int N=2e6+7,mod=1e9+7;
int z[N],s[N],e[N],p[N];
set<pair<int,int>> st;
int main(){
ios:: sync_with_stdio(0),cin.tie(0),cout.tie(0);
int n,x,y;
cin>>n;
for(int i=0;i<n;i++){
cin>>x>>y;
e[x]=y;
s[y]=x;
}
for(int i=1;i<=2*n;i++){
if(e[i]){
st.insert(mk(e[i],i));
auto it=st.find(mk(e[i],i));
if(it==st.begin()) z[i]=2;
else{
z[i]=1;
auto it2=st.begin();
it--;
for(;it2!=it;){
int g=it2->S;
z[g]=min(z[g],1);
it2++;
if(p[g] && p[g]!=(it2->S)) z[i]=0;
p[g]=(it2->S);
if(g<(it2->S)) z[i]=0;
}
}
}
else{
st.erase(mk(i,s[i]));
}
}
ll ans=1;
for(int i=1;i<=2*n;i++){
if(e[i]) ans=ans*(ll)z[i]%mod;
}
cout<<ans<<endl;
}
