#include <bits/stdc++.h>
using namespace std;
using pint = pair<int, int>;
const int MOD = 1e9 + 7;
int main() {
int n;
cin >> n;
int x[n << 1], seen[n + 1]{}, other[n + 1];
for (int i = 1; i <= n; ++i) {
int l, r;
cin >> l >> r;
x[--l] = x[--r] = i;
}
vector<int> adj[n + 1];
vector<pint> v;
for (int i = 0; i < (n << 1); ++i) {
if (seen[x[i]]++) {
pint agg{-1, 0};
for (; other[x[i]] < other[v.back().first]; v.pop_back()) {
adj[x[i]].emplace_back(v.back().first);
adj[v.back().first].emplace_back(x[i]);
agg.second += v.back().second;
agg.first = v.back().first;
}
if (not --v.back().second) v.pop_back();
if (~agg.first) v.push_back(agg);
} else {
v.emplace_back(x[i], 1);
other[x[i]] = i;
}
}
int c[n + 1]{};
function<void(int)> dfs = [&] (int i) {
for (int j: adj[i]) {
if (c[j]) continue;
c[j] = 3 - c[i];
dfs(j);
}
};
int ans = 1;
for (int i = 1; i <= n; ++i) {
if (c[i]) continue;
c[i] = 1;
dfs(i);
ans = (ans << 1) % MOD;
}
stack<int> st[3];
for (int xi: x) {
if (seen[xi]++ == 2) st[c[xi]].emplace(xi);
else if (st[c[xi]].top() != xi) {
cout << "0\n";
return 0;
} else st[c[xi]].pop();
}
cout << ans << endl;
}
