#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr int MOD = 1e9+7;
pair<int, int> operator + (const pair<int, int> &x, const pair<int, int> &y){return pair<int, int>(x.first + y.first, x.second + y.second);}
pair<int, int> operator - (const pair<int, int> &x, const pair<int, int> &y){return pair<int, int>(x.first - y.first, x.second - y.second);}
struct Seg{
pair<int, int> tree[2002000];
int sz;
void init(int n){sz = n;}
void update(int p, int x){
pair<int, int> v(1, x);
while(p<=sz){
tree[p] = tree[p] + v;
p += p&-p;
}
}
pair<int, int> sum(int p){
pair<int, int> ret(0, 0);
while(p){
ret = ret + tree[p];
p -= p&-p;
}
return ret;
}
int query(int l, int r){
auto p = sum(r) - sum(l-1);
if (p.second==0 && p.first) return 1;
else if (p.second==0) return -2;
if (p.second==p.first) return 0;
return -1;
}
}tree;
struct DSU{
int path[2002000], R[2002000], c;
void init(int n){c = n; for (int i=1;i<=n;i++) path[i] = R[i] = i;}
int find(int s){
if (s==path[s]) return s;
return path[s] = find(path[s]);
}
void merge(int s, int v){
s = find(s), v = find(v);
if (s==v) return;
--c;
path[s] = v;
R[v] = max(R[v], R[s]);
}
int r(int x){return R[find(x)];}
}dsu;
vector<int> adj[2002000];
int a[2002000], visited[2002000], col[2002000];
ll pw(ll a, ll e){
if (!e) return 1;
ll ret = pw(a, e/2);
if (e&1) return ret * ret % MOD * a % MOD;
return ret * ret % MOD;
}
void dfs(int s, int pa = 0){
col[a[s]] = col[s];
visited[s] = 1;
for (auto &v:adj[s]) if (v!=pa){
col[v] = col[s] ^ 1;
dfs(v, s);
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
int n;
cin >> n;
tree.init(n*2);
dsu.init(n*2);
for (int i=1;i<=n;i++){
int x, y;
cin >> x >> y;
a[x] = y;
a[y] = x;
dsu.merge(x, y);
}
vector<int> st;
for (int i=1;i<=n*2;i++){
while(!st.empty() && st.back() < i) st.pop_back();
if (i < a[i]){
while(!st.empty() && st.back() < a[i]){
dsu.merge(a[i], st.back());
adj[a[i]].push_back(st.back());
adj[st.back()].push_back(a[i]);
st.pop_back();
}
st.push_back(dsu.r(i));
}
else{
int R = dsu.r(i);
while(!st.empty() && st.back() < R){
dsu.merge(i, st.back());
adj[i].push_back(st.back());
adj[st.back()].push_back(i);
st.pop_back();
}
}
}
for (int i=1;i<=n*2;i++) if (a[i] < i && !visited[i]) dfs(i);
for (int i=1;i<=n*2;i++) if (i < a[i]){
int tmp = tree.query(i, a[i]);
if (tmp!=col[i] && tmp!=-2){
printf("0\n");
return 0;
}
tree.update(a[i], col[i]);
}
printf("%lld\n", pw(2, dsu.c));
}
