#include <bits/stdc++.h>
using namespace std;
#define int long long
#define sp << ' ' <<
#define nl << '\n'
const int MOD = 1e9+7, MAXN = 1e6, INF = 1e18;
struct SegmentTree{
using T = array<int, 2>;
vector<T> a; int sz = 1; T ID = {-INF, -1};
void init(vector<T> &v){
while(sz < (int)v.size()) sz += sz;
a.assign(2*sz, ID);
build(v, 0, 0, sz);
}
void build(vector<T> &v, int x, int lx, int rx){
if(rx-lx==1){
if(lx < (int)v.size()) a[x] = v[lx];
return;
}
int mx = (lx + rx) / 2;
build(v, 2*x+1, lx, mx);
build(v, 2*x+2, mx, rx);
a[x] = max(a[2*x+1], a[2*x+2]);
}
void update(int i, int x, int lx, int rx){
if(rx-lx==1) return void(a[x] = ID);
int mx = (lx + rx) / 2;
if(i < mx) update(i, 2*x+1, lx, mx);
else update(i, 2*x+2, mx, rx);
a[x] = max(a[2*x+1], a[2*x+2]);
}
void update(int i){ update(i, 0, 0, sz); }
T rangeMax(int l, int r, int x, int lx, int rx){
if(r<=lx || rx<=l) return ID;
if(l<=lx && rx<=r) return a[x];
int mx = (lx + rx) / 2;
return max(rangeMax(l, r, 2*x+1, lx, mx), rangeMax(l, r, 2*x+2, mx, rx));
}
T rangeMax(int l, int r){ return rangeMax(l, r+1, 0, 0, sz); }
} st0, st1;
bitset<MAXN> vis, c;
int a[MAXN], b[MAXN];
void dfs(int u){
int v;
vis[u] = 1;
st0.update(a[u]);
st1.update(b[u]);
while((v = st0.rangeMax(a[u], b[u])[1]) >= 0){
if(b[v] < b[u]) break;
c[v] = c[u] ^ 1;
dfs(v);
}
while((v = st1.rangeMax(a[u], b[u])[1]) >= 0){
if(a[v] > a[u]) break;
c[v] = c[u] ^ 1;
dfs(v);
}
}
signed main(){
cin.tie(0)->sync_with_stdio(0);
int n; cin >> n;
int s[n+n];
vector<array<int, 2>> v0(n+n, {-INF, -1}), v1(n+n, {-INF, -1});
for(int i=0; i<n; ++i){
cin >> a[i] >> b[i]; --a[i], --b[i];
s[a[i]] = s[b[i]] = i;
v0[a[i]] = {b[i], i};
v1[b[i]] = {-a[i], i};
}
st0.init(v0), st1.init(v1);
int cnt = 1;
for(int i=0; i<n; ++i){
if(vis[i]) continue;
cnt = (cnt + cnt) % MOD;
dfs(i);
}
vector<int> curr[2];
for(int i=0; i<n+n; ++i){
int j = s[i];
if(a[j] == i){
curr[c[j]].push_back(j);
}else{
if(curr[c[j]].back() != j){
cout << 0;
return 0;
}else curr[c[j]].pop_back();
}
}
cout << cnt;
}
