/*
* In the name of God
*
* Author: Farbod Doost
* Last Modified: Sun, 06 Nov 2022 (12:08:19)
*
*/
#include <iostream>
#include <vector>
using namespace std;
const int N = 2e6 + 5;
const long long mod = 1e9 + 7;
int n, l[N], r[N], a[N];
bool vis[N], out[N];
int sz[N], par[N];
vector <int> adj[N], v;
long long pw(int a, int r)
{
if (r == 0)
return 1;
if (r == 1)
return a;
long long c = pw(a, r / 2);
return c * c % mod * pw(a, r % 2) % mod;
}
int get(int v)
{
if (v == par[v])
return v;
return par[v] = get(par[v]);
}
vector <int> vec;
void merge(int u, int v)
{
u = get(u), v = get(v);
for (auto x: adj[v])
vec.push_back(x);
par[v] = u, sz[u] += sz[v];
return;
}
signed main()
{
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> l[i] >> r[i];
a[l[i]] = i, a[r[i]] = -i;
}
for (int i = 1; i <= 2 * n; i++) {
if (a[i] > 0) {
par[a[i]] = a[i], sz[a[i]] = 1, adj[a[i]].push_back(a[i]), v.push_back(a[i]);
continue;
}
while (out[adj[get(-a[i])].back()])
adj[get(-a[i])].pop_back();
if (adj[get(-a[i])].back() != -a[i])
return cout << 0, 0;
while (v.back() != get(-a[i])) {
merge(get(-a[i]), v.back());
if (sz[v.back()] > 1)
return cout << 0, 0;
v.pop_back();
}
while (vec.size())
adj[get(-a[i])].push_back(vec.back()), vec.pop_back();
sz[get(-a[i])]--;
if (sz[get(-a[i])] == 0)
v.pop_back();
out[-a[i]] = 1;
}
int ans = 0;
for (int i = 1; i <= n; i++)
if (!vis[get(i)])
vis[get(i)] = 1, ans++;
cout << pw(2, ans);
return 0;
}
