#include <bits/stdc++.h>
#define int long long
using namespace std;
struct UnionFind
{
vector<int> id;
UnionFind(int N) : id(N, -1) {}
int find(int i)
{
return id[i] < 0 ? i : id[i] = find(id[i]);
}
void merge(int a, int b)
{
a = find(a), b = find(b);
if (a == b) return;
if (id[a] > id[b]) {assert(false); swap(a, b);}
id[a] += id[b];
id[b] = a;
}
};
const int MOD = 1e9 + 7;
signed main(void)
{
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int nbConteneurs;
cin >> nbConteneurs;
vector<pair<int, int>> conteneurs(nbConteneurs);
for (auto &[deb, fin] : conteneurs)
{
cin >> deb >> fin;
--deb, --fin;
}
sort(conteneurs.begin(), conteneurs.end());
vector<int> event(2*nbConteneurs);
for (int i(0); i < nbConteneurs; ++i)
event[conteneurs[i].first] = event[conteneurs[i].second] = i;
vector<priority_queue<int, vector<int>, greater<int>>> pqCC(nbConteneurs);
auto comp = [&](int i, int j)
{
return pqCC[i].top() > pqCC[j].top();
};
vector<bool> vu(nbConteneurs);
UnionFind uf(nbConteneurs);
priority_queue<int, vector<int>, decltype(comp)> ccEnVies(comp);
vector<int> block(2 * nbConteneurs, -1);
for (int iCont(0); iCont < nbConteneurs; ++iCont)
{
auto [deb, fin] = conteneurs[iCont];
int curCC = iCont;
pqCC[curCC].push(fin);
while (!ccEnVies.empty())
{
int iCC = ccEnVies.top(); ccEnVies.pop();
// On vire les inutiles :
if (pqCC[iCC].top() < deb)
{
while (!pqCC[iCC].empty() and pqCC[iCC].top() < deb)
pqCC[iCC].pop();
if (!pqCC[iCC].empty())
ccEnVies.push(iCC);
continue;
}
// On a plus d'aretes :
if (pqCC[iCC].top() > fin)
{
ccEnVies.push(iCC);
break;
}
block[iCont] = event[pqCC[iCC].top()];
// On a une arete :
// On fusionne les cc
if (uf.id[curCC] > uf.id[iCC])
swap(curCC, iCC);
uf.merge(curCC, iCC);
assert(uf.find(curCC) == curCC);
while (!pqCC[iCC].empty())
{
pqCC[curCC].push(pqCC[iCC].top());
pqCC[iCC].pop();
}
}
ccEnVies.push(curCC);
}
vector<int> side(nbConteneurs);
stack<int> stk[2];
for (int t(0); t < 2 * nbConteneurs; ++t)
{
int id = event[t];
if (vu[id])
{
if (stk[side[id]].top() != id)
{
cout << 0 << endl;
return 0;
}
stk[side[id]].pop();
continue;
}
vu[id] = true;
if (block[id] == -1)
side[id] = 0;
else
side[id] = !side[block[id]];
stk[side[id]].push(id);
}
assert(false);
int nbCC(0);
for (int i(0); i < nbConteneurs; ++i)
nbCC += uf.id[i] < 0;
int ret = 1;
for (int i(0); i < nbCC; ++i)
ret = (ret * 2) % MOD;
cout << ret << endl;
}
