#include<iostream>
#include<stdio.h>
#include<vector>
#include<cmath>
#include<queue>
#include<string.h>
#include<map>
#include<set>
#include<stack>
#include<algorithm>
#define ll long long
#define pi pair < ll,ll >
#define mp(a,b) make_pair(a,b)
#define mid (low+high)/2
#define rep(i,a,b) for(int i = a;i < b;i++)
#define N 2000004
#define INF 1e9+7
using namespace std;
ll n,mod=1e9+7;
pi ar[N];
ll seg[4*N][2];
bool vis[N];
ll col[N];
ll points[N];
vector < ll > graph[N];
void init(ll low,ll high,ll pos)
{
seg[pos][0]=2*n+1;
seg[pos][1]=0;
if(low==high)
return;
init(low,mid,pos*2+1);
init(mid+1,high,pos*2+2);
return;
}
void update(ll low,ll high,ll pos,ll slow,ll val,ll id)
{
if(low==high&&low==slow)
{
seg[pos][id]=val;
return;
}
if(low>slow||high<slow)
return;
update(low,mid,pos*2+1,slow,val,id);
update(mid+1,high,pos*2+2,slow,val,id);
seg[pos][0]=min(seg[pos*2+1][0],seg[pos*2+2][0]);
seg[pos][1]=max(seg[pos*2+1][1],seg[pos*2+2][1]);
return;
}
ll query(ll low,ll high,ll pos,ll slow,ll shigh,ll id)
{
//cout << low << " " << high << " " << pos << " " << slow<< " " << shigh << " " << id << " " << seg[pos][id] << endl;
if(low>=slow&&high<=shigh)
return seg[pos][id];
if(low>shigh||high<slow)
{
if(id==1)
return 0;
return 2*n+1;
}
if(id==1)
return max(query(low,mid,pos*2+1,slow,shigh,id),query(mid+1,high,pos*2+2,slow,shigh,id));
else
return min(query(low,mid,pos*2+1,slow,shigh,id),query(mid+1,high,pos*2+2,slow,shigh,id));
}
void dfs(ll cur,ll c)
{
if(vis[cur])
return;
col[cur] = c;
vis[cur]=true;
update(0,2*n,0,ar[cur].second,2*n+1,0);
update(0,2*n,0,ar[cur].first,0,1);
// cout << "here " << cur << " " << c << endl;
// find left intersections
ll q = query(0,2*n,0,ar[cur].first,ar[cur].second,0);
while(q < ar[cur].first)
{
q=points[q];
dfs(q,!c);
q = query(0,2*n,0,ar[cur].first,ar[cur].second,0);
}
// find right intersections
q = query(0,2*n,0,ar[cur].first,ar[cur].second,1);
while(q > ar[cur].second)
{
q=points[q];
dfs(q,!c);
q = query(0,2*n,0,ar[cur].first,ar[cur].second,1);
}
// cout << "out " << cur << " " << c << endl;
return;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n;
rep(i,0,n)
{
cin >> ar[i].first >> ar[i].second;
}
init(0,2*n,0);
rep(i,0,n)
{
points[ar[i].first]=points[ar[i].second]=i;
update(0,2*n,0,ar[i].second,ar[i].first,0);
update(0,2*n,0,ar[i].first,ar[i].second,1);
}
ll ans = 1;
rep(i,0,n)
{
if(!vis[i])
ans=(ans*2)%mod;
dfs(i,0);
}
stack < ll > s[2];
rep(i,1,2*n+1)
{
ll ind = points[i];
if(ar[ind].first==i)
{
s[col[ind]].push(ind);
}
else
{
if(s[col[ind]].top() != ind)
{
ans=0;
break;
}
else
s[col[ind]].pop();
}
}
cout << ans << endl;
return 0;
}
/*
4
1 5
2 6
3 4
7 8
*/
