#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e6+10;
const int mod = 1e9+7;
typedef long long ll;
int a[maxn], b[maxn];
int open[maxn], close[maxn];
int main(void)
{
int n;
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> a[i] >> b[i];
open[a[i]] = i, close[b[i]] = i;
}
ll ans = 1LL;
set<int> S;
priority_queue<int, vector<int>, greater<int> > fila;
fila.push(2*n+1); fila.push(2*n+2);
for (int i = 1; i <= 2*n; i++)
{
if (open[i])
{
int x = fila.top(); fila.pop();
int y = fila.top();
if (b[open[i]] < x && b[open[i]] < y)
ans = (ans*2)%mod;
else if (b[open[i]] > x && b[open[i]] > y)
{
ans = 0;
break;
}
fila.push(x); fila.push(b[open[i]]);
}
else
{
int x = fila.top(); fila.pop();
if (b[close[i]] == x) continue;
else fila.pop();
fila.push(x);
}
}
cout << ans << "\n";
}
