#define here cerr<<"===========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#include "bits/stdc++.h"
//#include <ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
#define ld double
#define ll long long
#define llinf 100000000000000000LL // 10^17
#define pb push_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define sz(a) (ll)(a.size())
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define cer(a) {cerr<<#a<<": ";for(ll x_ : a) cerr<<x_<< " ";cerr<<endl;}
#define daj_mi_malo_vremena ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
using namespace std;
#define maxn 1000005
#define mod 1000000007
ll n;
pll a[maxn];
pll t[4*maxn];
ll t2[4*maxn],lazy[4*maxn];
ll ans = 1;
void upd(ll v,ll tl,ll tr,ll i,pll p){
if(tl==tr){t[v] = p;return;}
ll mid = (tl+tr)/2;
if(i<=mid) upd(2*v,tl,mid,i,p);
else upd(2*v+1,mid+1,tr,i,p);
t[v] = max(t[2*v],t[2*v+1]);
}
pll get(ll v,ll tl,ll tr,ll l,ll r){
if(l>r) return {0,0};
if(tl==l&&tr==r) return t[v];
ll mid = (tl+tr)/2;
return max(get(2*v,tl,mid,l,min(mid,r)),get(2*v+1,mid+1,tr,max(mid+1,l),r));
}
void push(ll v,ll tl,ll tr){
t2[v]+=(tr-tl+1)*lazy[v];
if(tl<tr){
lazy[2*v]+=lazy[v];
lazy[2*v+1]+=lazy[v];
}
lazy[v] = 0;
}
void upd(ll v,ll tl,ll tr,ll l,ll r,ll x){
push(v,tl,tr);
if(l>r) return;
if(tl==l&&tr==r){
lazy[v]+=x;
push(v,tl,tr);
return;
}
ll mid = (tl+tr)/2;
upd(2*v,tl,mid,l,min(mid,r),x);
upd(2*v+1,mid+1,tr,max(mid+1,l),r,x);
t2[v] = t2[2*v]+t2[2*v+1];
}
ll get2(ll v,ll tl,ll tr,ll l,ll r){
push(v,tl,tr);
if(l>r) return 0;
if(tl==l&&tr==r) return t2[v];
ll mid = (tl+tr)/2;
return get2(2*v,tl,mid,l,min(mid,r)) + get2(2*v+1,mid+1,tr,max(mid+1,l),r);
}
bool vis[maxn];
bool cmp(ll x,ll y){
return a[x].sc-a[x].fi<a[y].sc-a[y].fi;
}
int main()
{
cout<<0<<endl;
return 0;
cin >> n;
for(ll i = 1;i<=n;i++) cin >> a[i].fi >> a[i].sc;
sort(a+1,a+1+n);
for(ll i = 1;i<=n;i++) upd(1,1,2*n,a[i].fi,{a[i].sc,i});
queue<ll> q;
vector<ll> v;
for(ll i = 1;i<=n;i++){
if(vis[i]) continue;
q.push(i);
upd(1,1,2*n,a[i].fi,{0,0});
while(sz(q)){
ll j = q.front();
q.pop();
v.clear();
vis[j] = 1;
ll l = a[j].fi,r = a[j].sc;
while(1){
pll p = get(1,1,2*n,l,r);
if(p.fi<r) break;
ll x = p.sc;
v.pb(x);
q.push(x);
upd(1,1,2*n,a[x].fi,{0,0});
}
for(ll x : v) upd(1,1,2*n,a[x].fi,a[x].sc,1);
sort(all(v),cmp);
ll last = 0,lastsz = 0,cnt = sz(v);
for(ll x : v){
ll cur = get2(1,1,2*n,a[x].fi,a[x].sc);
if(cur!=last+cnt*(a[x].sc-a[x].fi+1-lastsz)){
cout<<0<<endl;
return 0;
}
last = cur;
lastsz = a[x].sc-a[x].fi+1;
cnt--;
}
for(ll x : v) upd(1,1,2*n,a[x].fi,a[x].sc,-1);
}
ans*=2;
if(ans>=mod) ans%=mod;
}
cout<<ans<<endl;
return 0;
}
/*
4
1 3
2 5
4 8
6 7
ans: 4
3
1 4
2 5
3 6
ans: 0
5
1 4
2 10
6 9
7 8
3 5
ans: 8
8
1 15
2 5
3 8
4 6
14 16
7 9
10 13
11 12
ans: 16
*/
