/* _In The Name Of God_ */
#include <bits/stdc++.h>
using namespace std;
#define maxs(a, b) a = max(a, b)
#define mins(a, b) a = min(a, b)
#define pb push_back
#define F first
#define S second
#define mid ((l + r)/2)
// #define int long long
typedef pair<int, int> pii;
typedef long long ll;
const ll MOD = 1e9 + 7; // 998244353;
const int MXN = 1e6 + 2;
const int LOG = 21;
ll Pow(ll a, ll b) { return !b ? 1 : (Pow(a*a %MOD, b/2) * (b&1 ? a : 1)) %MOD; }
int n, N, Root, R[2*MXN], p[2*MXN];
vector<int> adj[MXN*LOG];
vector<int> h[LOG];
// bool mark[MXN*LOG], valid[MXN*LOG], col[MXN*LOG];
short m[MXN*LOG];
ll ans = 1;
void dfs(int v) {
m[v] |= 1;
// cout << v << '\n';
for (int u : adj[v]) {
int o = u < 0, j = abs(u);
if ((m[j]&2) && !(m[j]&1)) {
m[j] |= ((m[v]>>2) ^ o)<<2;
dfs(j);
}
else if ((m[j]&2) && (m[v]>>2) != ((m[j]>>2)^o)) ans = 0;
}
}
int Build(int l=1, int r=2*n+1, int H = 0) {
if (r - l < 2) {
return p[l];
}
int x = Build(l, mid, H+1);
int y = Build(mid, r, H+1);
++N; //lc[N] = x, rc[N] = y;
adj[N].pb(x);
adj[N].pb(y);
h[H].pb(N);
return N;
}
void AddE(int s, int e, int x, int l=1, int r=2*n+1, int id = Root) {
if (s <= l && r <= e) {
adj[id].pb(-x);
adj[x].pb(-id);
return;
}
if (s < mid) AddE(s,e,x, l, mid, adj[id][0]);
if (mid < e) AddE(s,e,x, mid, r, adj[id][1]);
}
int Rem(int s, int l = 1, int r=2*n+1, int id = Root, int H = 0) {
if (r - l < 2) {
return 0;
}
if (s < mid) {
int x = Rem(s, l, mid, adj[id][0], H+1);
++N;
adj[N].pb(x);
adj[N].pb(adj[id][1]);
}
else {
int x = Rem(s, mid, r, adj[id][1], H+1);
++N;
adj[N].pb(adj[id][0]);
adj[N].pb(x);
}
h[H].pb(N);
return N;
}
void _solve() {
cin >> n;
N = n;
for (int i = 1; i <= n; i++) {
int l, r;
cin >> l >> r;
R[r] = l;
p[l] = i;
}
Root = Build();
for (int i = 1; i <= 2*n; i++) {
if (R[i]) {
AddE(R[i]+1, i+1, p[R[i]]);
Root = Rem(R[i]);
}
}
fill(m+1, m+n+1, 2);
for (int i = 0; i < LOG; i++) {
for (int j : h[i]) {
if (adj[j].size() > 2)
m[j] = 2;
m[abs(adj[j][0])] |= m[j];
m[abs(adj[j][1])] |= m[j];
}
}
for (int i = n + 1; i <= N; i++) {
if (m[i]) {
if (adj[i][0] != 0)
adj[abs(adj[i][0])].pb(i);
if (adj[i][1] != 0)
adj[abs(adj[i][1])].pb(i);
// cout << i << ' ' << adj[i][0].F << '\n';
// cout << i << ' ' << adj[i][1].F << '\n';
}
}
// for (int i = 1; i <= n; i++) {
// for (int j : adj[i]) cout << i << ' ' << j.F << '\n';
// }
m[0] = 0;
for (int i = LOG-1; i >= 0; i--) {
for (int j : h[i]) {
if (m[j] && !m[abs(adj[j][0])] && !m[abs(adj[j][1])]) m[j] = 0;
}
}
// cout << '\n';
for (int i = 1; i <= n; i++) {
if (!(m[i]&1) && (2&m[i])) dfs(i), (ans *= 2) %= MOD;
}
cout << ans << '\n';
}
int32_t main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
int _ = 1;
// cin >> _;
while (_--) _solve();
return 0.0;
}
