/*\ In The Name Of GOD
* Beyrad :D
\*/
#include "bits/stdc++.h"
#define sz(x) ((int) (x).size())
using namespace std;
const int N = 1e6 + 11, mod = 1e9 + 7;
int pw[N], mk[N], f[2 * N];
bitset<2 * N> sf;
vector<int> g[N];
bool bad;
void dfs(int u, int c) {
mk[u] = c;
for (int v : g[u]) {
if (mk[v] == -1)
dfs(v, c ^ 1);
else if (mk[v] == mk[u])
bad = 1;
}
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0), cout.tie(0);
memset(mk, -1, sizeof mk);
pw[0] = 1;
for (int i = 1; i < N; i++)
pw[i] = pw[i - 1] * 2 % mod;
int n;
cin >> n;
for (int i = 0; i < n; i++) {
int a, b;
cin >> a >> b;
--a, --b;
sf[a] = 0, sf[b] = 1;
f[a] = f[b] = i;
}
vector<int> st;
for (int i = 0; i < 2 * n; i++) {
if (sf[i] == 0) {
st.push_back(f[i]);
} else {
vector<int> tmp;
while (!st.empty() && st.back() != f[i]) {
g[f[i]].push_back(st.back());
g[st.back()].push_back(f[i]);
tmp.push_back(st.back());
st.pop_back();
}
st.pop_back();
while (!tmp.empty())
st.push_back(tmp.back()), tmp.pop_back();
}
}
bad = 0;
int cnt = 0;
for (int i = 0; i < n; i++) {
if (mk[i] == -1)
dfs(i, 0), cnt++;
}
if (bad)
return cout << 0 << '\n', 0;
cout << pw[cnt] << '\n';
return 0;
}
