This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define LCBorz ios_base::sync_with_stdio(false); cin.tie(0);
#define int long long
#define all(x) x.begin(), x.end()
#define endl '\n'
const int N=200005;
const int INF=1e18;
const int mod=1e9+7;
vector<int> adj[N],vis(N),dis(N);
void dfs(int k,int pa){
vis[k]=1;
for(int j:adj[k]){
if(j==pa)continue;
if(!vis[j]){
dis[j]=dis[k]+1;
dfs(j,k);
}
else if(dis[j]%2==dis[k]%2){
cout<<0<<endl;
exit(0);
}
}
}
int32_t main() {
LCBorz;
int n;cin>>n;
vector<int> a(n),b(n);
for(int i=0;i<n;i++){
cin>>a[i]>>b[i];
}
for(int i=0;i<n;i++){
for(int j=0;j<n;j++){
if(i==j)continue;
int cnt=(a[j]>=a[i]&&a[j]<=b[i])+(b[j]>=a[i]&&b[j]<=b[i]);
if(cnt==1){
adj[i].push_back(j);
}
}
}
int ans=1;
for(int i=0;i<n;i++){
if(!vis[i]){
ans=ans*2%mod;
dfs(i,i);
}
}
cout<<ans<<endl;
return 0;
}
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