#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define F first
#define S second
#define forn(i, n) for(int i = 0; i < n; ++i)
#define forbn(i, b, n) for(int i = b; i < n; ++i)
#define sz(v) (int)v.size()
#define pb push_back
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define mp make_pair
#define at(m, p) (m.find(p) != m.end() ? m[p] : 0)
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef long long ll;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
template <class T> inline void mineq(T &a, T b) { a = min(a, b); }
template <class T> inline void maxeq(T &a, T b) { a = max(a, b); }
const long long mod = 1000 * 1000 * 1000 + 7;
inline long long mpow(long long b, long long ex) {
long long r = 1;
while(ex) {
if(ex & 1)
r = (r * b) % mod;
ex = ex >> 1;
b = (b * b) % mod;
}
return r;
}
struct Seg {
int n;
vector<set<int>> sl;
void init(int n, vi &vals) {
this->n = n;
sl.resize(2 * n);
forn(i, n) {
sl[i + n].insert(vals[i]);
}
for(int i = n - 1; i > 0; i--) {
sl[i].insert(all(sl[2 * i]));
sl[i].insert(all(sl[2 * i + 1]));
}
}
void add(vi &nb, int v, int val, bool is_left) {
auto it = sl[v].lower_bound(val);
if(is_left) {
copy(it, sl[v].end(), back_inserter(nb));
} else {
copy(sl[v].begin(), it, back_inserter(nb));
}
}
void query(vi &nb, int l, int r, int bd, bool is_left) {
for(l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
if(l & 1)
add(nb, l++, bd, is_left);
if(r & 1)
add(nb, --r, bd, is_left);
}
}
void del(int p, int val) {
for(p += n; p > 0; p >>= 1)
sl[p].erase(val);
}
};
vector<int> att;
int ncomps = 0;
vi l2r, e2i;
vii vlr;
Seg seg;
int ch(int c) {
return c == 1 ? 2 : 1;
}
void my_push(queue<ii> &q, int node, int color) {
int l = vlr[node].F, r = vlr[node].S;
seg.del(l, r);
seg.del(r, l);
q.push({node, color});
att[node] = color;
}
void bfs(int root) {
ncomps += 1;
queue<ii> q;
my_push(q, root, 1);
while(!q.empty()) {
int node = q.front().F, color = q.front().S;
int L = vlr[node].F, R = vlr[node].S;
q.pop();
vi nbs;
seg.query(nbs, L + 1, R - 1, R, true);
seg.query(nbs, L + 1, R - 1, L, false);
for(int nb: nbs) {
my_push(q, e2i[nb], ch(color));
}
}
}
void solve() {
int n;
cin >> n;
l2r.resize(2 * n);
e2i.resize(2 * n);
att.assign(n, 0);
forn(i, n) {
int l, r;
cin >> l >> r;
l--; r--;
l2r[l] = r;
l2r[r] = l;
e2i[l] = e2i[r] = i;
vlr.eb(l, r);
}
seg.init(2 * n, l2r);
forn(i, n) {
if(!att[i]) {
bfs(i);
}
}
stack<int> st[2];
bool bad = false;
forn(e, 2 * n) {
int i = e2i[e], c = att[i] - 1;
if(vlr[i].F == e) {
st[c].push(i);
} else {
if(st[c].top() != i) {
bad = true;
break;
} else {
st[c].pop();
}
}
}
cout << (bad ? 0 : mpow(2, ncomps)) << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
// freopen("gathering.in", "r", stdin);
// freopen("gathering.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--) {
solve();
}
}
