#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> Pair;
const int Nmax = 2e6 + 5, Mod = 1e9 + 7;
priority_queue < Pair, vector<Pair>, greater<Pair> > heap;
int i, n, x, y;
int where[Nmax], in[Nmax];
vector<Pair> v[5];
int ans = 1;
bool verif(vector<Pair> &v)
{
while(heap.size()) heap.pop();
for(auto it : v)
{
while(heap.size() && heap.top().first < it.first) heap.pop();
if(heap.size() && heap.top().first < it.second) return 0;
heap.push({it.second, -1});
}
return 1;
}
int main()
{
// freopen("input", "r", stdin);
cin.sync_with_stdio(false);
cin >> n;
for(i=1; i<=n; ++i)
{
cin >> x >> y;
in[x] = y;
}
for(i=1; i<=2*n; ++i) if(in[i])
{
while(heap.size() && heap.top().first < i) heap.pop();
if(heap.size() && heap.top().first < in[i])
{
where[i] = 3 - where[heap.top().second];
v[where[i]].push_back({i, in[i]});
heap.push({in[i], i});
continue;
}
where[i] = 1;
v[1].push_back({i, in[i]});
heap.push({in[i], i});
ans = ans * 2 % Mod;
}
if(!verif(v[1]) || !verif(v[2])) cout << 0 << '\n';
else cout << ans << '\n';
return 0;
}
