//#pragma GCC optimize("Ofast,unroll-loops")
//#pragma GCC target("arch=icelake-server,avx512f,avx512bw,avx512bitalg,bmi,bmi2")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
constexpr ll mod = 1e9 + 7;
vector<int> sgt1[5000000];
vector<int> sgt2[5000000];
void update1(int v,int l,int r, int pos,int val){
if(pos > r or pos < l) return;
sgt1[v].push_back(val);
if(l == r) {
return;
}
int mid = (l+r)/2;
update1(v*2,l,mid,pos,val);
update1(v*2+1,mid+1,r,pos,val);
}
void update2(int v,int l,int r, int pos,int val){
if(pos > r or pos < l) return;
sgt2[v].push_back(val);
if(l == r) {
return;
}
int mid = (l+r)/2;
update2(v*2,l,mid,pos,val);
update2(v*2+1,mid+1,r,pos,val);
}
vector<int> tmp;
void get(int v,int l,int r,int tl,int tr) {
if(tl > r or tr < l) return;
if(tl <= l and tr >= r) {
while(!sgt1[v].empty() and sgt1[v].back() < tl) {
tmp.push_back(sgt1[v].back());
sgt1[v].pop_back();
}
while(!sgt2[v].empty() and sgt2[v].back() > tr) {
tmp.push_back(sgt2[v].back());
sgt2[v].pop_back();
}
return;
}
int m = (l+r)/2;
get(v*2,l,m,tl,tr);
get(v*2+1,m+1,r,tl,tr);
}
int O[3000001];
int C[3000001];
pair<int,int> A[3000001];
int B[3000001];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
ll n;
cin >> n;
for (int i = 0; i < n; ++i) {
int l,r;
cin >> l >> r;
A[i] = {l,r};
B[l] = i;
B[r] = i;
O[l] = r;
O[r] = l;
}
for (int i = 2*n; i >= 1;i--) {
if(O[i] > i)
update1(1, 1, 2 * n, O[i], i);
}
for (int i = 1; i <= 2*n;i++) {
if(O[i] < i)
update2(1, 1, 2 * n, O[i], i);
}
int cnt = 0;
for(int i = 0; i < n;i++) {
if(C[i]) continue;
cnt++;
vector<int> c1;
vector<int> c2;
queue<pair<int,int>> Q;
Q.emplace(i,1);
while(!Q.empty()) {
auto [v,c] = Q.front();
Q.pop();
if(C[v] == c) continue;
if(C[v] and C[v] != c) {
cout << 0 << "\n";
return 0;
}
C[v] = c;
if(c == 1) {
c1.push_back(v);
} else {
c2.push_back(v);
}
tmp.clear();
get(1,1,2*n,A[v].first,A[v].second);
for(auto e:tmp) {
Q.emplace(B[e],-c);
}
}
vector<int> starts1;
for(auto e:c1) starts1.push_back(A[e].first);
vector<int> starts2;
for(auto e:c2) starts2.push_back(A[e].first);
sort(starts1.begin(),starts1.end());
sort(starts2.begin(),starts2.end());
stack<int> S;
for(auto e:starts1) {
while(!S.empty() and O[S.top()] < e) {
S.pop();
}
if(!S.empty() and O[S.top()] < O[e]) {
cout << 0 << "\n";
return 0;
}
}
for(auto e:starts2) {
while(!S.empty() and O[S.top()] < e) {
S.pop();
}
if(!S.empty() and O[S.top()] < O[e]) {
cout << 0 << "\n";
return 0;
}
}
}
ll ans = 1;
for (int i = 0; i < cnt;i++) {
ans *= 2;
ans %= mod;
}
cout << ans << "\n";
return 0;
}
