#include <bits/stdc++.h>
#define int long long
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
#define kill(x) cout << x << "\n", exit(0);
#define pii pair<int, int>
#define pll pair<long long, long long>
#define endl "\n"
using namespace std;
typedef long long ll;
// typedef __int128_t lll;
typedef long double ld;
const int MAXN = (int)20 + 7;
const int MOD = (int)1e9 + 7;
const ll INF = (ll)1e18 + 7;
const int LG = 30;
int n, m, k, tmp, t, tmp2, tmp3, tmp4, u, v, w, flag, q, ans, N, res, pre_ans;
pii arr[MAXN];
bool seen[MAXN], col[MAXN], st[MAXN];
vector<pair<int, bool>> adj[MAXN];
inline void add_edge(int u, int v, bool x) {
// cout << "! " << u << " " << v << " " << x << endl;
adj[u].pb({v, x});
adj[v].pb({u, x});
}
/* Segment Tree */
#define mid ((l+r)>>1)
#define lid (id<<1)
#define rid (lid|1)
vector<int> seg[MAXN<<2];
int ptr[MAXN<<2];
void add_seg(int s, int x, int l=0, int r=MAXN, int id=1) {
if (l+1 == r) {
seg[id].pb(x);
return;
}
if (s < mid) add_seg(s, x, l, mid, lid);
else add_seg(s, x, mid, r, rid);
}
void build(int l=0, int r=MAXN, int id=1) {
ptr[id] = -1;
if (l+1 == r) {
sort(all(seg[id]));
return;
}
build(l, mid, lid);
build(mid, r, rid);
seg[id].resize(seg[lid].size()+seg[rid].size());
merge(all(seg[lid]), all(seg[rid]), seg[id].begin());
}
void check(int s, int t, int x, int l=0, int r=MAXN, int id=1) {
if (s >= t) return;
if (s <= l && t >= r) {
if (seg[id].empty() || seg[id][0] > x) return;
add_edge(seg[id][0], x, 1);
while (ptr[id]+1 < seg[id].size() && seg[id][ptr[id]+1] < x) ptr[id]++;
return;
}
if (s < mid) check(s, t, x, l, mid, lid);
if (t > mid) check(s, t, x, mid, r, rid);
}
inline void process(int id) {
for (int i=1; i<=ptr[id]; i++) add_edge(seg[id][0], seg[id][i], 0);
}
void rebuild(int l=0, int r=MAXN, int id=1) {
if (l+1 == r) {
process(id);
return;
}
rebuild(l, mid, lid);
rebuild(mid, r, rid);
process(id);
}
/* Segment Tree */
void DFS(int v) {
seen[v] = 1;
for (auto cur:adj[v]) {
int u = cur.F, w = cur.S;
if (!seen[u]) {
if (w == 1) col[u] = 1-col[v];
else col[u] = col[v];
DFS(u);
} else if ((w == 1 && col[u] == col[v]) || (w == 0 && col[u] != col[v])) kill(0);
}
}
int32_t main() {
#ifdef LOCAL
freopen("inp.in", "r", stdin);
freopen("res.out", "w", stdout);
#else
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#endif
cin >> n;
for (int i=1; i<=n; i++) {
cin >> arr[i].F >> arr[i].S;
st[arr[i].F] = 1; add_seg(arr[i].S, arr[i].F);
}
build();
for (int i=1; i<=n; i++) check(arr[i].F, arr[i].S, arr[i].F);
rebuild();
ans = 1;
for (int i=1; i<MAXN; i++) {
if (seen[i] || !st[i]) continue;
DFS(i);
ans = (ans+ans)%MOD;
}
cout << ans << endl;
return 0;
}
