#include <bits/stdc++.h>
using namespace std;
const int N = 1'000'000 + 10;
int n;
pair<int, int> range[N];
namespace DSU {
int id[N], c[N];
void init() { memset(id, -1, sizeof id); }
int root(int u) {
if (id[u] < 0) return u;
int p = root(id[u]);
c[u] ^= c[id[u]];
return id[u] = p;
}
int join(int u, int v) {
int rootU = root(u), rootV = root(v);
if (id[rootU] > id[rootV]) swap(rootU, rootV);
if (rootU == rootV) return c[u] ^ c[v];
id[rootU] += id[rootV];
id[rootV] = rootU;
c[rootV] = c[u] ^ c[v] ^ 1;
return 1;
}
}
int type[N << 1], id[N << 1];
int32_t main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n;
for (int i = 1; i <= n; ++i) cin >> range[i].first >> range[i].second;
for (int i = 1; i <= n; ++i) {
type[range[i].first] = 1;
id[range[i].first] = id[range[i].second] = i;
}
DSU::init();
stack<list<int>> st;
for (int i = 1; i <= 2 * n; ++i) {
if (type[i]) st.push({id[i]});
else {
list<int> vt;
for (;;) {
if (st.top().back() == id[i]) {
st.top().pop_back();
if (!st.top().size()) st.pop();
break;
}
if (!DSU::join(id[i], st.top().back())) {
cout << 0 << "\n";
return 0;
}
vt.splice(vt.begin(), st.top());
st.pop();
}
if (vt.size()) st.push(vt);
}
}
int answer = 1;
for (int i = 1; i <= n; ++i) {
if (DSU::id[i] < 0) answer = 1ll * answer * 2 % 1'000'000'007;
}
cout << answer << "\n";
}
