//DUEL
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define x first
#define y second
#define pii pair<int,int>
#define pb push_back
#define eb emplace_back
#pragma GCC optimize("unroll-loops")
#define shandom_ruffle(a, b) shuffle(a, b, rng)
#define vi vector<int>
#define vl vector<ll>
#define popcnt __builtin_popcount
#define popcntll __builtin_popcountll
#define all(a) begin(a),end(a)
using namespace std;
using namespace __gnu_pbds;
using ll=long long;
using ull=unsigned long long;
using ld=long double;
int MOD=1000000007;
int MOD2=998244353;
vector<int> bases;
const ll LLINF=1ll<<60;
const char en='\n';
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void yes() {cout<<"YES"<<en; exit(0);}
void no() {cout<<"NO"<<en; exit(0);}
inline int rund() {int x576363482791fuweh=rng();return abs(x576363482791fuweh)%RAND_MAX;}
template<class T>
void prVec(vector<T> w,bool fl=false)
{
cout<<w.size()<<en;
for (int i=0;i<int(w.size())-1;++i) cout<<w[i]<<' ';
if (w.size()) cout<<w[w.size()-1]<<en;
if (fl) cout<<flush;
}
void M998()
{
swap(MOD,MOD2);
}
ll raand()
{
ll a=rund();
a*=RAND_MAX;
a+=rund();
return a;
}
#define rand raand
ll raaand()
{
return raand()*(MOD-7)+raand();
}
string to_upper(string a)
{
for (int i=0;i<(int)a.size();++i) if (a[i]>='a' && a[i]<='z') a[i]-='a'-'A';
return a;
}
string to_lower(string a)
{
for (int i=0;i<(int)a.size();++i) if (a[i]>='A' && a[i]<='Z') a[i]+='a'-'A';
return a;
}
ll sti(string a,int base=10)
{
ll k=0;
for (int i=0;i<(int)a.size();++i)
{
k*=base;
k+=a[i]-'0';
}
return k;
}
template<class T>
void eras(vector<T>& a,T b)
{
a.erase(find(a.begin(),a.end(),b));
}
string its(ll k,int base=10)
{
if (k==0) return "0";
string a;
while (k)
{
a.push_back((k%base)+'0');
k/=base;
}
reverse(a.begin(),a.end());
return a;
}
ll min(ll a,int b)
{
if (a<b) return a;
return b;
}
ll min(int a,ll b)
{
if (a<b) return a;
return b;
}
ll max(ll a,int b)
{
if (a>b) return a;
return b;
}
ll max(int a,ll b)
{
if (a>b) return a;
return b;
}
ll gcd(ll a,ll b)
{
if (b==0) return a;
return gcd(b,a%b);
}
ll lcm(ll a,ll b)
{
return a/gcd(a,b)*b;
}
template<class T,class K>
pair<T,K> mp(T a,K b)
{
return make_pair(a,b);
}
inline int mult(ll a,ll b)
{
return (a*b)%MOD;
}
inline int pot(int n,int k)
{
if (k==0) return 1;
ll a=pot(n,k/2);
a=mult(a,a);
if (k%2) return mult(a,n);
else return a;
}
int divide(int a,int b)
{
return mult(a,pot(b,MOD-2));
}
inline int sub(int a,int b)
{
if (a-b>=0) return a-b;
return a-b+MOD;
}
inline int add(int a,int b)
{
if (a+b>=MOD) return a+b-MOD;
return a+b;
}
bool prime(ll a)
{
if (a==1) return 0;
for (int i=2;i<=round(sqrt(a));++i)
{
if (a%i==0) return 0;
}
return 1;
}
const int N=2000010,M=1<<21;
int n,r[N],cn=100,don;
bool col[N];
pii xse[M*2+10];
int nse[M*2+10];
void rem(int i)
{
nse[r[i]+M]=MOD;
xse[i+M]={-1,-1};
for (int j=(i+M)/2;j;j/=2) xse[j]=max(xse[j*2],xse[j*2+1]);
for (int j=(r[i]+M)/2;j;j/=2) nse[j]=min(nse[j*2],nse[j*2+1]);
}
int ge1(int l,int r,int lo=0,int hi=M,int i=1)
{
//if (cn) --cn,cout<<l<<' '<<r<<' '<<lo<<' '<<hi<<' '<<i<<' '<<nse[i]<<endl;
if (lo>=l && hi<=r) return nse[i];
if (lo>=r || hi<=l) return MOD;
int mid=(lo+hi)/2;
return min(ge1(l,r,lo,mid,i*2),ge1(l,r,mid,hi,i*2+1));
}
pii ge2(int l,int r,int lo=0,int hi=M,int i=1)
{
//cout<<l<<' '<<r<<' '<<lo<<' '<<hi<<' '<<i<<' '<<xse[i].x<<' '<<xse[i].y<<en;
if (lo>=l && hi<=r) return xse[i];
if (lo>=r || hi<=l) return {-1,-1};
int mid=(lo+hi)/2;
return max(ge2(l,r,lo,mid,i*2),ge2(l,r,mid,hi,i*2+1));
}
void dfs(int i,bool chc=1)
{
rem(i);
auto a=ge2(i+1,r[i]);
while (a.x>r[i])
{
++don;
if (chc) col[a.y]=!col[i];
//if (cn) --cn,cout<<"m1 "<<i<<' '<<a.y<<en;
dfs(a.y,chc);
a=ge2(i+1,r[i]);
}
int b=ge1(i+1,r[i]);
while (b<i)
{
++don;
if (chc) col[b]=!col[i];
//if (cn) --cn,cout<<"m2 "<<i<<' '<<b<<en;
dfs(b,chc);
b=ge1(i+1,r[i]);
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
for (int i=0;i<10;++i) bases.push_back(rand()%(MOD-13893829*2)+13893829);
cin>>n;
for (int i=0;i<n;++i)
{
int a,b;
cin>>a>>b;
r[a]=b;
}
for (int i=M;i<M*2;++i) nse[i]=MOD,xse[i]={-1,-1};
for (int i=1;i<=2*n;++i) if (r[i]) nse[r[i]+M]=i,xse[i+M]={r[i],i};
for (int i=M-1;i;--i) nse[i]=min(nse[i*2],nse[i*2+1]),xse[i]=max(xse[i*2],xse[i*2+1]);
int cc=0;
for (int i=1;i<=2*n;++i) if (r[i] && xse[i+M]!=mp(-1,-1))
{
//cout<<"dfs("<<i<<")"<<endl;
++cc;
dfs(i);
}
for (int i=M;i<M*2;++i) nse[i]=MOD,xse[i]={-1,-1};
for (int i=1;i<=2*n;++i) if (r[i] && col[i]) nse[r[i]+M]=i,xse[i+M]={r[i],i};
for (int i=M-1;i;--i) nse[i]=min(nse[i*2],nse[i*2+1]),xse[i]=max(xse[i*2],xse[i*2+1]);
vi nc;
for (int i=1;i<=2*n;++i) if (r[i] && col[i]) nc.pb(i);
don=0;
for (auto i: nc) if (r[i] && !don) dfs(i,0);
if (don==0)
{
for (int i=M;i<M*2;++i) nse[i]=MOD,xse[i]={-1,-1};
for (int i=1;i<=2*n;++i) if (r[i] && !col[i]) nse[r[i]+M]=i,xse[i+M]={r[i],i};
for (int i=M-1;i;--i) nse[i]=min(nse[i*2],nse[i*2+1]),xse[i]=max(xse[i*2],xse[i*2+1]);
vi nc;
for (int i=1;i<=2*n;++i) if (r[i] && !col[i]) nc.pb(i);
don=0;
for (auto i: nc) if (r[i] && !don) dfs(i,0);
if (don==0) cout<<pot(2,cc)<<en;
else cout<<0<<en;
}
else cout<<0<<en;
}
