#include <bits/stdc++.h>
#define pii pair<int, int>
#define mp make_pair
#define F first
#define S second
#define PB push_back
#define FOR(i, u, v) for (int i = u; i <= v; i++)
#define FORD(i, v, u) for (int i = v; i >= u; i--)
#define ll long long
#define mid (r + l)/2
#define N 200005
#define LN 19
#define maxc 1000000007
using namespace std;
int n, pos[N], a[N], dd[N];
pii seg[N];
struct IntervalTree
{
int tmin[N << 2], tmax[N << 2];
void calc(int id)
{
tmin[id] = min(tmin[id*2], tmin[id*2+1]);
tmax[id] = max(tmax[id*2], tmax[id*2+1]);
}
void build(int l, int r, int id)
{
if (l == r)
{
tmin[id] = tmax[id] = a[l];
return;
}
build(l, mid, id*2);
build(mid+1, r, id*2+1);
calc(id);
}
void disable(int l, int r, int id, int x)
{
if (l == r)
{
tmin[id] = maxc; tmax[id] = 0;
return;
}
if (x <= mid) disable(l, mid, id*2, x);
else disable(mid+1, r, id*2+1, x);
calc(id);
}
int getMin(int l, int r, int id, int x, int y)
{
if (l > y || r < x) return maxc;
if (l >= x && r <= y) return tmin[id];
return min(getMin(l, mid, id*2, x, y), getMin(mid+1, r, id*2+1, x, y));
}
int getMax(int l, int r, int id, int x, int y)
{
if (l > y || r < x) return 0;
if (l >= x && r <= y) return tmax[id];
return max(getMax(l, mid, id*2, x, y), getMax(mid+1, r, id*2+1, x, y));
}
}t;
void stop() {cout <<0; exit(0);}
void DFS(int u, int col)
{
dd[u] = col;
t.disable(1, 2*n, 1, seg[u].F);
t.disable(1, 2*n, 1, seg[u].S);
while (1)
{
int l = t.getMin(1, 2*n, 1, seg[u].F, seg[u].S);
if (l >= seg[u].F) break;
int v = pos[l];
if (dd[v] != -1)
if (dd[v] != (col^1)) stop();
DFS(v, col^1);
}
while (1)
{
int r = t.getMax(1, 2*n, 1, seg[u].F, seg[u].S);
if (r <= seg[u].S) break;
int v = pos[r];
if (dd[v] != -1)
if (dd[v] != (col^1)) stop();
DFS(v, col^1);
}
}
bool check()
{
stack<int> v[2];
FOR(i, 1, 2*n)
{
int u = pos[i];
int type = dd[u];
if (i == seg[u].F) v[type].push(u);
else
{
if (v[type].top() != u) return 0;
v[type].pop();
}
}
return 1;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
//freopen("INP.TXT", "r", stdin);
cin >> n;
FOR(i, 1, n)
{
int u, v; cin >> u >> v;
seg[i] = mp(u, v);
}
sort(seg+1, seg+n+1);
FOR(i, 1, n)
{
int u = seg[i].F, v = seg[i].S;
a[u] = v; a[v] = u;
pos[u] = pos[v] = i;
}
t.build(1, 2*n, 1);
memset(dd, -1, sizeof dd);
int res = 1;
FOR(i, 1, n)
{
if (dd[i] != -1) continue;
DFS(i, 0);
res = (res*2) % maxc;
}
if (check()) cout <<res;
else stop();
}
