#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define fi first
#define se second
#define pb push_back
#define int long long
#define sz(a) (int)a.size()
#define all(a) begin(a),end(a)
#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
using ll = long long;
using vi = vector<int>;
using ar2 = array<int,2>;
using ar3 = array<int,3>;
const int mxN = (int)1e6+10;
const int INF = (int)1e9;
const ll LINF = (ll)2e18;
const int MOD = (int)1e9+7;
int n, a[mxN], SZ, cnt[mxN];
template<int SZ>
struct WeightedDsu{
int p[SZ], sz[SZ], w[SZ], cc;
void init(int n){
cc = 0;
for(int i = 1; i <= n; i++)
p[i]=i,sz[i]=1,w[i]=0,cc++;
}
int findSet(int i){
if(i==p[i]) return i;
int par = findSet(p[i]);
w[i]^=w[p[i]];
return p[i]=par;
}
void unionSet(int i, int j){
int x = findSet(i), y = findSet(j);
if(x==y){
if(w[i]^w[j]^1){
cout << 0 << "\n";
exit(0);
}
return;
}
if(sz[x]<sz[y])swap(x,y);
cc--; w[y]=w[x]^w[y]^1;
sz[x]+=sz[y]; p[y]=x;
}
};
WeightedDsu<mxN> dsu;
int poww(int a, int b){
if(!b) return 1;
int x = poww(a,b/2);
x*=x,x%=MOD;
if(b&1)x*=a,x%=MOD;
return x;
}
int32_t main()
{
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n; SZ=n; dsu.init(n);
for(int i = 0; i < n; i++){
int x, y; cin >> x >> y;
a[x]=a[y]=i;
}
set<pair<int,int>> S;
for(int i = 1; i <= 2*n; i++){
if(cnt[a[i]]){
S.erase({cnt[a[i]],a[i]});
auto itr = S.lower_bound(make_pair(cnt[a[i]],-1));
while(itr!=S.end()){
dsu.unionSet(itr->se,a[i]); itr++; SZ--;
}
}
else S.insert({i,a[i]}),cnt[a[i]]=i;
}
cout << poww(2,SZ);
}
