#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e6+6, MOD = 1e9+7;
int n;
pair<int,int> nums[N];
int mark[2*N], match[2*N];
bool badr[N];
set<pair<int,int>> hast, nol, nor;
vector<int> G[N];
bool is[N];
void DFS(int v) {
is[v] = 1;
for (int u : G[v]) {
if (!is[u]) {
DFS(u);
}
}
}
void solve() {
cin >> n;
for (int i = 1;i <= n;i++) {
cin >> nums[i].first >> nums[i].second;
mark[nums[i].first] = i;
mark[nums[i].second] = i;
match[nums[i].first] = nums[i].second;
match[nums[i].second] = nums[i].first;
}
for (int i = 1;i <= 2*n;i++) {
if (match[i] > i) {
hast.insert({i,mark[i]});
nol.insert({i,mark[i]});
nor.insert({i,mark[i]});
} else {
if (nor.find({match[i],mark[i]}) == nor.end()) {
cout << 0;
return;
}
vector<pair<int,int>> rem;
for (auto it = nor.lower_bound({match[i],mark[i]});it != nor.end();it++) {
auto it2 = hast.find(*it);
int v = it2->second;
if (badr[v] && v != mark[i]) {
cout << 0;
return;
}
it2++;
if (it2 != hast.end()) {
G[v].push_back(it2->second);
rem.push_back(*it);
}
}
for (auto val : rem) nor.erase(val);
rem.clear();
for (auto it = nol.upper_bound({match[i],mark[i]});it != nol.end();it++) {
auto it2 = hast.find(*it);
int v = it2->second;
if (it2 != hast.begin()) {
it2--;
G[v].push_back(it2->second);
rem.push_back(*it);
}
}
for (auto val : rem) {
nol.erase(val);
}
rem.clear();
auto it = hast.find({match[i],mark[i]});
if (nol.find({match[i],mark[i]}) == nol.end()) {
it--;
badr[it->second] = 1;
it++;
}
it++;
if (it != hast.end()) {
nol.insert(*it);
}
it--;
if (it != hast.begin()) {
it--;
nor.insert(*it);
}
nol.erase({match[i],mark[i]});
nor.erase({match[i],mark[i]});
hast.erase({match[i],mark[i]});
}
// cout << i << endl;
// cout << "hast : ";
// for (auto val : hast) {
// cout << val.first << ' ' << val.second << " - ";
// }
// cout << '\n';
// cout << "nor : ";
// for (auto val : nor) {
// cout << val.first << ' ' << val.second << " - ";
// }
// cout << '\n';
// cout << "nol : ";
// for (auto val : nol) {
// cout << val.first << ' ' << val.second << " - ";
// }
// cout << '\n';
}
int c = 0;
for (int i = 1;i <= n;i++) {
if (!is[i]) {
DFS(i);
c++;
}
}
int ans = 1;
for (int i = 0;i < c;i++) {
ans = (ans*2)%MOD;
}
cout << ans;
}
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
}
