// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
using namespace std;
#define nl '\n'
const int MOD = 1e9+7;
int main() {
cin.tie(0)->sync_with_stdio(0);
int N; cin >> N;
int P = N;
vector<int> E(2*N);
for(int i = 0; i < N; i++) {
int a, b; cin >> a >> b; --a, --b;
E[a] = b;
E[b] = -1;
}
set<int> S;
for(int x = 0; x < 2*N; x++) {
if (E[x] == -1) {
S.erase(x);
} else {
int v = E[x];
int amt = 0;
for(const auto &c : S) {
if (c < v) amt++;
else break;
if (amt == 2) break;
}
// cout << v << " " << amt << nl;
if (amt == 2) {
cout << 0 << nl;
return 0;
}
if (amt == 1) P--;
S.insert(v);
}
}
int ans = 1;
for(int i = 0; i < P; i++) ans = (2 * ans) % MOD;
cout << ans << nl;
return 0;
}
