#include<bits/stdc++.h>
using namespace std;
#define int long long
struct dsu {
int n, cc;
vector<int> r, s, d;
dsu(int n) {
this->n=n; cc=n;
r.reserve(n+1);
for (int i = 1; i <= n; ++i) r[i]=i;
s.assign(n+1, 1);
d.assign(n+1, 0);
}
int find(int a) {
if (a==r[a]) return a;
int p=find(r[a]);
d[a]^=d[r[a]];
return r[a]=p;
}
bool unite(int a, int b) {
int ra=find(a), rb=find(b);
if (ra==rb) return d[a]^d[b]==1;
if (s[ra]<s[rb]) swap(ra, rb);
d[rb]=1^d[a]^d[b];
r[rb]=ra; s[ra]+=s[rb]; cc--;
return true;
}
};
int exp(int a, int b, int mod) {
int x=1;
while (b) {
if (b%2) x=(x*a)%mod;
a=(a*a)%mod; b/=2;
} return x;
}
inline char nc(){
static char buf[100000],*p1=buf,*p2=buf;
return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline void read(int &x){
char c=nc(); x=0;
for(;c>'9'||c<'0';c=nc());for(;c>='0'&&c<='9';x=x*10+c-'0',c=nc());
}
signed main() {
cin.tie(0)->sync_with_stdio(false);
int n, a, b; read(n);
vector<int> e(2*n+1);
for (int i = 0; i < n; ++i) {
read(a); read(b);
e[a]=i+1;
e[b]=-i-1;
}
dsu uf(n+1);
list<int> tmp;
stack<list<int>> mt;
for (auto i = 1; i <= 2*n; ++i) {
if (e[i]>0) {
mt.push({});
mt.top().push_back(e[i]);
} else {
e[i]=-e[i];
tmp.clear();
while (true) {
if (mt.top().back()==e[i]) {
mt.top().pop_back();
if (mt.top().size()==0) mt.pop();
break;
}
if (!uf.unite(e[i], mt.top().back())) { cout << "0\n"; return 0; }
tmp.splice(tmp.begin(), mt.top());
mt.pop();
}
if (tmp.size()) {
mt.push({});
mt.top().splice(mt.top().begin(), tmp);
}
}
}
cout << exp(2, uf.cc-1, 1e9+7) << '\n';
return 0;
}
