// In the name of Allah
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef complex<ld> cld;
#define all(x) (x).begin(),(x).end()
#define len(x) ((ll) (x).size())
#define F first
#define S second
#define X real()
#define Y imag()
#define pb push_back
#define sep ' '
#define endl '\n'
#define Mp make_pair
#define kill(x) cout << x << '\n', exit(0)
#define set_dec(x) cout << fixed << setprecision(x);
#define file_io(x,y) freopen(x, "r", stdin); freopen(y, "w", stdout);
struct node {
pair<pii, int> val1, val2;
};
int n;
const int maxn = 2e6 + 4;
const int mod = 1e9 + 7;
pii A[maxn]; int ind[maxn], num;
pii p[maxn]; vector<int> ls[maxn];
node t[4 * maxn], ca;
ll power(ll a, ll b) {
if (b == 0) return 1;
return power(a * a % mod, b / 2) * ((b & 1) ? a : 1) % mod;
}
node f(node a, node b) {
node res = a;
for (auto x : {b.val1, b.val2}) {
if (x.S != -1) {
if (res.val1.S == -1 || x.F != res.val1.F) {
res.val2 = res.val1; res.val1 = x;
}
}
}
return res;
}
void build(int v, int tl, int tr) {
t[v] = ca;
if (tr - tl == 1) return ;
int mid = (tl + tr) / 2;
build(2 * v + 1, tl, mid); build(2 * v + 2, mid, tr);
}
void set_val(int v, int tl, int tr, int i, pair<pii, int> x) {
if (i >= tr || i < tl) return ;
if (tr - tl == 1) {
t[v].val1 = x;
return ;
}
int mid = (tl + tr) / 2;
set_val(2 * v + 1, tl, mid, i, x); set_val(2 * v + 2, mid, tr, i, x);
t[v] = f(t[2 * v + 1], t[2 * v + 2]);
}
node get_res(int v, int tl, int tr, int l, int r) {
l = max(l, tl); r = min(r, tr);
if (l >= tr || r <= tl) return ca;
if (l == tl && r == tr) return t[v];
int mid = (tl + tr) / 2;
return f(get_res(2 * v + 1, tl, mid, l, r), get_res(2 * v + 2, mid, tr, l, r));
}
void merge(int u1, int u2) {
pii a = p[u1], b = p[u2];
if (a.F == b.F) {
if (a.S == b.S) kill(0);
return ;
}
num--;
if (len(ls[a.F]) > len(ls[b.F])) swap(a, b);
int r = (a.S == b.S);
for (int v : ls[a.F]) {
p[v].F = b.F; p[v].S ^= r;
ls[b.F].pb(v);
set_val(0, 0, 2 * n, A[v].F, Mp(p[v], v));
}
ls[a.F].clear(); ls[a.F].shrink_to_fit();
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ca.val1 = ca.val2 = Mp(Mp(-1, -1), -1);
cin >> n;
for (int i = 0; i < n; i++) {
cin >> A[i].F >> A[i].S;
A[i].F--; A[i].S--;
ind[A[i].F] = i; ind[A[i].S] = i;
}
num = n;
for (int i = 0; i < n; i++) {
p[i] = Mp(i, 0);
ls[i].pb(i);
}
build(0, 0, 2 * n);
for (int j = 2 * n - 1; j >= 0; j--) {
int i = ind[j];
if (A[i].S != j) continue;
auto f = get_res(0, 0, 2 * n, A[i].F + 1, A[i].S);
while (f.val2.S != -1) {
merge(i, f.val1.S); merge(i, f.val2.S);
f = get_res(0, 0, 2 * n, A[i].F + 1, A[i].S);
}
if (f.val1.S != -1) merge(i, f.val1.S);
set_val(0, 0, 2 * n, A[i].F, Mp(p[i], i));
}
cout << power(2, num) << endl;
return 0;
}
