#include<bits/stdc++.h>
#define taskname "B"
using namespace std;
const int mod = 1e9 + 7;
int n;
namespace sub1{
void solve(){
vector<int>a(n), b(n), p(n << 1 | 1);
for(int i = 0; i < n; i++){
cin >> a[i] >> b[i];
p[b[i]] = -(p[a[i]] = i + 1);
}
int ans = 1 << n;
for(int mask = (1 << n) - 1; mask > -1; mask--){
vector<stack<int>>st(2);
for(int i = 1; i <= (n << 1); i++){
bool bit = bool(mask >> (abs(p[i]) - 1) & 1);
if(p[i] > 0){
st[bit].push(p[i]);
}
else{
if(st[bit].top() != -p[i]){
ans--;
break;
}
st[bit].pop();
}
}
}
cout << ans;
}
}
namespace sub2{
void solve(){
vector<int>a(n), b(n);
vector<vector<int>>g(n);
auto inside = [&] (int i, int l, int r){
return l < i && r > i;
};
for(int i = 0; i < n; i++){
cin >> a[i] >> b[i];
for(int j = 0; j < i; j++){
if((inside(a[j], a[i], b[i]) && inside(b[i], a[j], b[j])) || (inside(a[i], a[j], b[j]) && inside(b[j], a[i], b[i]))){
g[i].emplace_back(j);
g[j].emplace_back(i);
}
}
}
vector<int>color(n, -1);
int ans = 1;
auto dfs = [&] (auto&& self, int s) -> void{
for(int& d : g[s]){
if(color[d] == -1){
color[d] = color[s] ^ 1;
self(self, d);
}
else if(color[s] == color[d]){
cout << 0;
exit(0);
}
}
};
for(int i = 0; i < n; i++){
if(color[i] == -1){
color[i] = 0;
dfs(dfs, i);
ans = (ans << 1) % mod;
}
}
cout << ans;
}
}
namespace sub34{
const int lim = 1e6 + 5;
int p[lim << 2], r[lim << 1];
int find_set(int N){
return N == p[N] ? N : p[N] = find_set(p[N]);
}
void merge(int u, int v){
p[find_set(u)] = find_set(v);
}
void solve(){
memset(r, 0, sizeof(r));
for(int i = 0; i < n; i++){
int l;
cin >> l >> r[l];
}
iota(p + 1, p + (n << 2) + 1, 1);
set<int>s;
for(int i = 1; i <= (n << 1); i++){
if(r[i] > 0){
for(auto it = s.lower_bound(i), bound_r = s.lower_bound(r[i]); it != bound_r; it = next(it)){
merge(*it, r[i] + (n << 1));
merge(*it + (n << 1), r[i]);
if(find_set(*it) == find_set(*prev(bound_r))){
break;
}
}
s.insert(r[i]);
}
}
int ans = 1;
for(int i = 1; i <= (n << 1); i++){
if(r[i] > 0){
if(find_set(r[i]) == find_set(r[i] + (n << 1))){
return void(cout << 0);
}
if(r[i] == find_set(r[i])){
ans = (ans << 1) % mod;
}
}
}
cout << ans;
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if(fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
}
cin >> n;
if(n <= 20){
sub1::solve();
}
else if(n <= 2000){
sub2::solve();
}
else{
sub34::solve();
}
}
