#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007
int main(){
int n, l, r;
cin>>n;
vector<int> ev(2 * n + 1, 0);
for (int i = 1; i <= n; i++){
cin>>l>>r;
ev[l] = i;
ev[r] = -i;
}
bool can = 1;
int nxt = 0;
vector<int> isd(n + 1, 0), la(n + 1, 0), de;
for (int i = 1; i <= 2 * n; i++){
while (!de.empty() && isd[de.back()] == 1) de.pop_back();
if (ev[i] > 0){
de.push_back(ev[i]);
continue;
}
int no = -ev[i], in = de.size() - 1;
if (la[no] == 0) nxt++;
while (de[in] != no){
if (la[de[in]] != 0 && isd[de[in]] == 0){
can = 0;
break;
}
la[de[in]] = 1;
in--;
}
if (!can) break;
isd[no] = 1;
}
if (!can){
cout<<0<<"\n";
return 0;
}
int ans = 1;
for (int i = 1; i <= nxt; i++) ans = (ans * 2) % mod;
cout<<ans;
}
