#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, 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]});
nor.insert({i,mark[i]});
} else {
if (nor.find({match[i],mark[i]}) == nor.end()) {
cout << 0;
return;
}
vector<pair<int,int>> rem;
auto fix = hast.find({match[i],mark[i]});
fix++;
if (fix != hast.end()) {
G[mark[i]].push_back(fix->second);
G[fix->second].push_back(mark[i]);
badr[mark[i]] = 1;
}
for (auto it = nor.upper_bound({match[i],mark[i]});it != nor.end();it++) {
auto it2 = hast.find(*it);
int v = it->second;
it2++;
if (it2 != hast.end()) {
if (badr[v]) {
cout << 0;
return;
}
G[v].push_back(it2->second);
G[it2->second].push_back(v);
rem.push_back(*it);
}
}
for (auto val : rem) nor.erase(val);
auto nxt = fix;
fix--;
if (nxt != hast.end() && fix != hast.begin()) {
fix--;
auto prev = fix;
fix++;
if (badr[prev->second]) {
badr[prev->second] = 0;
nor.erase(*prev);
} else if (nor.find(*prev) == nor.end()) {
badr[prev->second] = 1;
nor.insert(*prev);
}
} else if (fix != hast.begin()) {
fix--;
badr[fix->second] = 0;
nor.insert(*fix);
}
badr[mark[i]] = 0;
hast.erase({match[i],mark[i]});
nor.erase({match[i],mark[i]});
}
// cout << i << '\n';
// 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 << "badr : ";
// for (int i = 1;i <= n;i++) {
// cout << i << ',' << badr[i] << " ";
// }
// 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();
}
