#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#ifdef _WIN32
#define getchar_unlocked _getchar_nolock
#endif
//#define int long long
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define ppb pop_back
#define eb emplace_back
#define g0(a) get<0>(a)
#define g1(a) get<1>(a)
#define g2(a) get<2>(a)
#define g3(a) get<3>(a)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef double db;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef tuple<int, int, int, int> iiii;
typedef tree<ii, null_type, less<ii>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
int N, ans, L[1000005], R[1000005], link[1000005], sz[1000005], r[1000005];
bool inv, vis[1000005], col[1000005], cl[1000005];
vector<int> adj[1000005];
vector<ii> curr;
set<int> Aseg, Bseg;
const int MOD = 1e9 + 7;
bool is(int a, int b) {
if (L[a] > L[b]) return is(b, a);
return R[b] > R[a] && R[a] > L[b];
}
int find(int x) {
if (x == link[x]) return x;
return link[x] = find(link[x]);
}
void unite(int a, int b) {
a = find(a);
b = find(b);
if (a == b) return;
if (sz[b] > sz[a]) swap(a, b);
sz[a] += sz[b];
link[b] = a;
}
void dfs(int n) {
vis[n] = 1;
for (auto u : adj[n])
if (vis[u]) {
if (col[u] == col[n]) inv = 1;
} else {
col[u] = col[n] ^ 1;
dfs(u);
}
}
main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> N;
for (int i = 1; i <= N; i++) {
link[i] = i;
sz[i] = 1;
cin >> L[i] >> R[i];
cl[R[i]] = 1;
r[L[i]] = r[R[i]] = i;
}
for (int i = 1; i <= 2 * N; i++) {
if (!cl[i]) {
bool A = 0, B = 0;
auto it = Aseg.lower_bound(L[r[i]]);
if (it != Aseg.end() && *it < R[r[i]]) A = 1;
it = Bseg.lower_bound(L[r[i]]);
if (it != Bseg.end() && *it < R[r[i]]) B = 1;
if (A && B) return cout << "0\n", 0;
else if (A) Bseg.insert(R[r[i]]);
else Aseg.insert(R[r[i]]);
}
}
for (int i = 1; i <= 2 * N; i++) {
if (cl[i]) {
int pos = -1, cnt = 0;
for (int j = (int)curr.size() - 1; j >= 0; j--) {
if (find(r[i]) == find(curr[j].first)) {
pos = j;
break;
} else unite(r[i], curr[j].first), cnt += curr[j].second;
}
if (pos == -1) while (1) {}
for (int k = 0, run = curr.size() - pos; k < run - 1; k++) curr.ppb();
curr.back().second += cnt - 1;
if (curr.back().second == 0) curr.ppb();
} else {
curr.eb(r[i], 1);
}
}
if (inv) cout << "0\n";
else {
ans = 1;
for (int i = 1; i <= N; i++)
if (i == find(i)) ans *= 2, ans %= MOD;
cout << ans << '\n';
}
}
