#include<bits/stdc++.h>
using namespace std;
const int MAXN=2e6+5;
const int mod=1e9+7;
const int INF=1e9;
int fen[MAXN],pos[MAXN],dsu[MAXN];
bool ck[MAXN];
vector<int> vi[MAXN];
int getlog(long long n) { return 63-__builtin_clzll(n); }
void update(int i,int n,int val) { for(;i<=n;i+=i&-i) fen[i]+=val; }
int get(int i) { int ans=0;for(;i;i-=i&-i) ans+=fen[i];return ans; }
int walk(int n,int val) { int ans=0;for(int i=getlog(n);i+1;i--) if(ans+(1<<i)<=n&&val>=fen[ans+(1<<i)]) val-=fen[ans+=(1<<i)];return ans+1; }
int root(int i)
{
if(!dsu[i]) return i;
return dsu[i]=root(dsu[i]);
}
bool merge(int i,int j)
{
bool c=(ck[i]==ck[j]);
if((i=root(i))==(j=root(j)))
{
if(c)
{
cout<<0;
exit(0);
}
return false;
}
if(vi[i].size()<vi[j].size()) swap(i,j);
if(c) for(auto v:vi[j]) ck[v]=1-ck[v];
for(auto v:vi[j]) vi[i].push_back(v);
vi[j].clear(),dsu[j]=i;
return true;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
for(int i=1;i<=n;i++)
{
int l,r;
cin>>l>>r;
pos[r]=l;
}
int cc=n,cnt=0;
for(int i=1;i<=n*2;i++) vi[i].push_back(i);
for(int i=n*2;i;i--) if(pos[i]>0)
{
int c=get(pos[i]),res;
while((res=walk(n*2,c))<=i)
{
if(++cnt>n*n) return cout<<0,0;
cc-=merge(pos[i],res),c++;
}
update(pos[i],n*2,1);
}
int ans=1;
for(int i=1;i<=cc;i++) ans=ans*2%mod;
cout<<ans;
}
