#include <bits/stdc++.h>
using namespace std;
#define finish(x) return cout << x << endl, 0
#define ll long long
const int N = 1000001;
int n, vis[N], p[N], mod = 1e9 + 7;
vector <pair <int, int> > a;
vector <int> f, v[N];
void dfs(int node){
for(auto &i : v[node]){
if(vis[i] != -1 && vis[i] != (vis[node] ^ 1)){
cout << 0 << endl;
exit(0);
}
if(vis[i] != -1) continue;
vis[i] = vis[node] ^ 1;
dfs(i);
}
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
memset(vis, -1, sizeof vis);
cin >> n;
a.resize(n);
f.resize(2 * n);
for(int i = 0 ; i < n ; i++){
cin >> a[i].first >> a[i].second;
a[i].first--; a[i].second--;
f[a[i].first] = f[a[i].second] = i;
p[i] = i;
}
vector <int> o, del(n);
for(int i = 0 ; i < 2 * n ; i++){
while(o.size() && del[o.back()]){
o.pop_back();
}
if(a[f[i]].first == i){
o.push_back(f[i]);
}
else{
del[f[i]] = 1;
int j = (int)o.size() - 1;
while(o[j] != f[i]){
if(del[o[j]] == 0){
v[f[i]].push_back(o[j]);
v[o[j]].push_back(f[i]);
}
j--;
}
}
}
int ans = 1;
for(int i = 0 ; i < n ; i++){
if(vis[i] != -1) continue;
ans *= 2;
if(ans >= mod) ans -= mod;
vis[i] = 0;
dfs(i);
}
cout << ans << endl;
}
