#include <bits/stdc++.h>
#define int long long
using namespace std;
#define sz(v) ((int)(v).size())
#define all(v) (v).begin(), (v).end()
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
std::mt19937 rng(std::chrono::steady_clock::now().time_since_epoch().count());
void solve() {
int n;cin>>n;
vector<int> pai(n);
iota(all(pai),0);
vector<int> ev(2*n);
vector<int> ini(n);
L(i,0,n-1){
int a,b;cin>>a>>b;a--;b--;
ev[a]=i;
ev[b]=i;
ini[i]=a;
}
vector<int> muda(n,0);
vector<int> tam(n,1);
auto find=[&](auto&& self, int node)->int{
if(node==pai[node])return node;
int x=self(self,pai[node]);
muda[node]^=muda[pai[node]];
pai[node]=x;
return pai[node];
};
auto uni=[&](int a, int b)->bool{
a=find(find,a);
b=find(find,b);
if(a==b){
if(muda[a]==muda[b])return false;
return true;
}
if(tam[a]<tam[b])swap(a,b);
pai[b]=a;
muda[b]=1;
tam[a]+=tam[b];
return true;
};
set<pair<int,int>> ativo;
L(i,0,2*n-1){
int at=ev[i];
if(ativo.find({ini[at],at})==ativo.end()){
ativo.insert({ini[at],at});
}
else{
ativo.erase({ini[at],at});
auto pt=ativo.lower_bound({ini[at],0});
while(pt!=ativo.end()){
int a=(*pt).second;
if(!uni(at,a)){
cout<<0;return;
}
pt++;
}
}
}
vector<int> ehp(n,0);
L(i,0,n-1){
ehp[find(find,i)]=1;
}
const int MOD=1e9+7;
int resp=1;
L(i,0,n-1){
if(ehp[i]){
resp*=2;
resp%=MOD;
}
}
cout<<resp;return;
}
int32_t main() {
std::cin.tie(0)->sync_with_stdio(0);
std::cin.exceptions(std::cin.failbit);
int T = 1;
// std::cin >> T;
while(T--) {
solve();
}
return 0;
}
