#include <iostream>
#include <vector>
#include <array>
#include <algorithm>
#include <map>
#define ll long long
using namespace std;
bool B[2000000];
vector <ll> V;
vector <array<ll, 2> > R, Q;
ll A[2000000], L[2000000], M = 1e9 + 7;
struct SegTree{
vector <ll> st[8000000];
vector <ll> st2[8000000];
void build(ll id, ll l, ll r) {
if (l == r) {
if (A[l] != -1) st[id].push_back(A[l]);
else st2[id].push_back(L[l]);
return;
}
ll mid = (l+r)/2;
build(id*2, l, mid);
build(id*2+1, mid+1, r);
int i = 0, j = 0;
while (i < st[id*2].size() && j < st[id*2+1].size()) {
if (st[id*2][i] < st[id*2+1][j]) st[id].push_back(st[id*2][i++]);
else st[id].push_back(st[id*2+1][j++]);
}
while (i < st[id*2].size()) st[id].push_back(st[id*2][i++]);
while (j < st[id*2+1].size()) st[id].push_back(st[id*2+1][j++]);
i = 0, j = 0;
while (i < st2[id*2].size() && j < st2[id*2+1].size()) {
if (st2[id*2][i] > st2[id*2+1][j]) st2[id].push_back(st2[id*2][i++]);
else st2[id].push_back(st2[id*2+1][j++]);
}
while (i < st2[id*2].size()) st2[id].push_back(st2[id*2][i++]);
while (j < st2[id*2+1].size()) st2[id].push_back(st2[id*2+1][j++]);
}
void query(ll id, ll l, ll r, ll ql, ll qr) {
if (qr < l || r < ql) return;
else if (ql <= l && r <= qr) {
while (!st[id].empty()) {
auto u = st[id].back();
if (B[u] || qr < u) {
if (!B[u]) {
R.push_back({L[u], u});
B[L[u]] = B[u] = 1;
}
st[id].pop_back();
}
else break;
}
while (!st2[id].empty()) {
auto u = st2[id].back();
if (B[u] || u < ql) {
if (!B[u]) {
R.push_back({u, A[u]});
B[u] = B[A[u]] = 1;
}
st2[id].pop_back();
}
else break;
}
return;
}
ll mid = (l+r)/2;
query(id*2, l, mid, ql, qr);
query(id*2+1, mid+1, r, ql, qr);
}
} ST;
ll n, a, b, f = 1;
int main() {
cin.tie(0);
ios::sync_with_stdio(0);
cin >> n;
for (int i=0; i<2*n; ++i) A[i] = L[i] = -1;
for (int i=0; i<n; ++i) {
cin >> a >> b;
--a, --b;
L[b] = a;
A[a] = b;
}
ST.build(1, 0, 2*n-1);
for (int i=0; i<2*n; ++i) {
if (!B[i]) {
f *= 2;
f %= M;
B[i] = B[A[i]] = 1;
R.clear();
Q.clear();
Q.push_back({i, A[i]});
while (true) {
for (auto [l, r] : Q) {
ST.query(1, 0, 2*n-1, l, r);
}
Q.clear();
V.clear();
if (R.empty()) break;
sort(R.begin(), R.end());
for (auto [x, y] : R) {
while (!V.empty() && V.back() < x) {
V.pop_back();
}
if (!V.empty() && V.back() < y) {
cout << "0\n";
return 0;
}
V.push_back(y);
}
swap(R, Q);
}
}
}
cout << f << '\n';
}
