#ifdef LOCKAL
#define _GLIBCXX_DEBUG
#endif
#ifndef LOCKAL
#pragma GCC optimize("Ofast")
#pragma GCC target("sse3,sse4")
#endif
#include <bits/stdc++.h>
//#define TIMUS
//#define FILENAME "journey"
#ifndef TIMUS
#include <ext/rope>
#include <ext/pb_ds/assoc_container.hpp>
#endif // TIMUS
#define all(x) x.begin(), x.end()
#define F first
#define S second
#define pb push_back
#define pii pair<int, int>
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
const int INF = INT_MAX / 2;
const ll LINF = (ll)2e18 + 666, M = 1e9 + 7;
const ld EPS = 1e-7;
#ifndef M_PI
const ld M_PI = acos(-1);
#endif // M_PI
using namespace std;
#ifndef TIMUS
using namespace __gnu_cxx;
using namespace __gnu_pbds;
template<class K, class T>
using ordered_map = tree<K, T, less<K>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#endif
void run();
template<class T1, class T2>
inline bool mini(T1 &a, T2 b)
{
if (a > b)
{
a = b;
return 1;
}
return 0;
}
template<class T1, class T2>
inline bool maxi(T1 &a, T2 b)
{
if (a < b)
{
a = b;
return 1;
}
return 0;
}
int main()
{
#ifndef LOCKAL
#ifdef FILENAME
freopen(FILENAME".in", "r", stdin);
freopen(FILENAME".out", "w", stdout);
#endif // FILENAME
#endif
#ifndef TIMUS
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
#endif // TIMUS
srand(time(0));
auto start = clock();
run();
#ifdef LOCKAL
//cout << endl;
cout << "\ntime = " << (ld)(clock() - start) / CLOCKS_PER_SEC << "\n";
#endif
return 0;
}
#define DEBUG
#if defined DEBUG && defined LOCKAL
#define debugdo(x) x
#else
#define debugdo(x)
#endif
#define debug(x) debugdo(cout << x << endl)
#define debug2(x) debugdo(cout << x << " ")
// ---SOLUTION--- //
void run()
{
int n;
cin >> n;
vector<int> e(n * 2), ap(n), bp(n);
for (int i = 0; i < n; i++)
{
int a, b;
cin >> a >> b;
e[a - 1] = i + 1;
e[b - 1] = -i - 1;
ap[i] = a - 1;
bp[i] = b - 1;
}
set<int> s;
vector<bool> c(n);
ll ans = 1;
for (int i = 0; i < n * 2; i++)
{
if (e[i] > 0)
{
int b = bp[e[i] - 1];
if (s.lower_bound(i) != s.end() && *s.lower_bound(i) < b)
{
c[e[i] - 1] = !c[-e[*s.lower_bound(i)] - 1];
}
else
{
ans *= 2;
ans %= M;
}
s.insert(bp[e[i] - 1]);
}
}
stack<int> a, b;
for (auto x: e)
{
if (x > 0)
{
if (c[x - 1])
a.push(x);
else
b.push(x);
}
else
{
x = -x;
if (c[x - 1])
{
if (a.top() != x)
{
cout << 0;
return;
}
a.pop();
}
else
{
if (b.top() != x)
{
cout << 0;
return;
}
b.pop();
}
}
}
cout << ans;
}
/*
*/
