#include <iostream> #include <vector> #include <set> #include <algorithm> using namespace std; int Mx[1<<21]; int main(){ int n, Ans = 1, mod = 1e9 + 7; cin>>n; vector<pair<int, int>> vec; for (int i=1, a, b;i<=n;i++){ cin>>a>>b; vec.push_back({a, b}); } sort(begin(vec), end(vec)); set<int> R; for (auto [l, r] : vec){ auto u = R.upper_bound(r); if (u != begin(R)) Mx[r] = *prev(u); if (Mx[r] > l) n--; if (Mx[r] != 0 and Mx[Mx[r]] > l) Ans = 0; R.insert(r); } while (n >= 30) Ans = (1LL * Ans + (1<<30)) % mod, n -= 30; cout<<1LL * Ans * (1<<n) % mod<<'\n'; }