#include <cstdio>
#include <algorithm>
#define SZ 2097152
#define pii pair<int,int>
using namespace std;
int n, chk[1010000];
int P[2010000];
pii IT[SZ+SZ][2];
struct point{
int b, e;
}w[1010000];
void Ins(int ck, int a, pii b){
a += SZ;
IT[a][ck] = b;
while(a!=1){
a>>=1;
if(ck) IT[a][ck] = min(IT[a+a][ck], IT[a+a+1][ck]);
else IT[a][ck] = max(IT[a+a][ck], IT[a+a+1][ck]);
}
}
pii Get(int ck, int b, int e){
b += SZ, e += SZ;
pii r;
if(ck) r = pii(n+n+1,0);
else r = pii(0,0);
while(b<=e){
if(ck) r = min(r, min(IT[b][ck], IT[e][ck]));
else r = max(r, max(IT[b][ck],IT[e][ck]));
b=(b+1)>>1,e=(e-1)>>1;
}
return r;
}
void DFS(int a, int col){
chk[a] = col;
int b = w[a].b, e = w[a].e;
Ins(0, b, pii(0,0));
Ins(1, e, pii(n+n+1,0));
while(1){
pii tp = Get(0, b+1, e-1);
if(tp.first < e)break;
DFS(tp.second, 3-col);
}
while(1){
pii tp = Get(1, b+1, e-1);
if(tp.first > b)break;
DFS(tp.second, 3-col);
}
}
int st[2010000];
bool Check(int a){
int i, top = 0;
for(i=1;i<=n+n;i++)P[i]=0;
for(i=1;i<=n;i++){
if(chk[i] == a)P[w[i].b] = i, P[w[i].e] = i;
}
for(i=1;i<=n+n;i++){
if(!P[i])continue;
if(top && st[top] == P[i])top--;
else st[++top] = P[i];
}
if(!top)return true;
return false;
}
int main(){
int i, res = 1;
scanf("%d",&n);
for(i=1;i<SZ+SZ;i++){
IT[i][0] = pii(0,0);
IT[i][1] = pii(n+n+1,0);
}
for(i=1;i<=n;i++){
scanf("%d%d",&w[i].b,&w[i].e);
Ins(0, w[i].b, pii(w[i].e, i));
Ins(1, w[i].e, pii(w[i].b, i));
}
for(i=1;i<=n;i++){
if(!chk[i]){
DFS(i,1);
res = res * 2 % 1000000007;
}
}
if(Check(1) && Check(2)){
printf("%d\n",res);
}
else printf("0\n");
}
