// 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);
int n;
const int maxn = 4000 + 4;
const int mod = 1e9 + 7;
pii A[maxn]; int ind[maxn];
int val[maxn]; set<pii> st;
int p[maxn], num;
int get(int a) {
return (p[a] == a) ? a : p[a] = get(p[a]);
}
void merge(int a, int b) {
a = get(a); b = get(b);
if (a == b) return ;
p[a] = b; num--;
}
ll power(ll a, ll b) {
if (b == 0) return 1;
return power(a * a % mod, b / 2) * ((b & 1) ? a : 1) % mod;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
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;
}
for (int j = 2 * n - 1; j >= 0; j--) {
int i = ind[j];
if (A[i].S == j) {
auto it = st.upper_bound(Mp(A[i].F, 2 * n));
if (it != st.end()) {
auto f = *it;
if (f.F < A[i].S) val[i] = f.S;
else val[i] = -1;
}
st.insert(Mp(A[i].F, i));
}
}
for (int i = 0; i < n; i++) {
if (val[i] == -1 || val[val[i]] == -1) continue;
int j = val[val[i]];
if (A[j].F > A[i].F && A[j].F < A[i].S && A[j].S > A[i].S) {
kill(0);
}
}
iota(p, p + n, 0); num = n;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (A[j].F > A[i].F && A[j].F < A[i].S && A[j].S > A[i].S) {
merge(i, j);
}
}
}
cout << power(2, num) << endl;
return 0;
}
