#include<bits/stdc++.h>
using namespace std;
const int NMAX = 1000009;
int N, M, a[NMAX], b[NMAX], p[2 * NMAX], pos[2 * NMAX], ap[NMAX];
const int mod = 1e9 + 7;
int ansMi, ansMa, hansMi, hansMa, mi[5 * NMAX], ma[5 * NMAX], hmi[5 * NMAX], hma[5 * NMAX];
void refresh (int nod, int f1, int f2)
{
mi[nod] = min (mi[f1], mi[f2]);
ma[nod] = max (ma[f1], ma[f2]);
hmi[nod] = (mi[nod] == mi[f1] ? hmi[f1] : hmi[f2]);
hma[nod] = (ma[nod] == ma[f1] ? hma[f1] : hma[f2]);
}
void build (int nod, int st, int dr)
{
if (st == dr)
{
if (p[st] == 0) mi[nod] = 4 * N, ma[nod] = 0;
else mi[nod] = ma[nod] = p[st];
hmi[nod] = hma[nod] = st;
return ;
}
int mij = (st + dr) >> 1, f1 = nod << 1, f2 = f1 | 1;
build (f1, st, mij);
build (f2, mij + 1, dr);
refresh (nod, f1, f2);
}
void query (int nod, int st, int dr, int x, int y)
{
if (x > y) return ;
if (x <= st && dr <= y)
{
if (mi[nod] < ansMi)
ansMi = mi[nod], hansMi = hmi[nod];
if (ma[nod] > ansMa)
ansMa = ma[nod], hansMa = hma[nod];
return ;
}
int mij = (st + dr) >> 1, f1 = nod << 1, f2 = f1 | 1;
if (x <= mij) query (f1, st, mij, x, y);
if (mij < y) query (f2, mij + 1, dr, x, y);
}
void delPos (int nod, int st, int dr, int pos)
{
if (st == dr)
{
mi[nod] = 4 * N, ma[nod] = 0;
return ;
}
int mij = (st + dr) >> 1, f1 = nod << 1, f2 = f1 | 1;
if (pos <= mij) delPos (f1, st, mij, pos);
else delPos (f2, mij + 1, dr, pos);
refresh (nod, f1, f2);
}
void delVal (int x)
{
delPos (1, 1, 2 * N, a[x]);
delPos (1, 1, 2 * N, b[x]);
}
void dfs (int nod, int c)
{
if (ap[nod] != 0 && ap[nod] != c)
{
printf ("0\n");
exit (0);
}
if (ap[nod] != 0) return ;
ap[nod] = c, delVal (nod);
while (1)
{
ansMi = 4 * N, ansMa = 0, query (1, 1, 2 * N, a[nod] + 1, b[nod] - 1);
if (ansMi > a[nod] && ansMa < b[nod]) break;
int toDel = 0;
if (ansMi <= a[nod]) toDel = pos[hansMi];
else toDel = pos[hansMa];
dfs (toDel, 3 - c);
}
}
void check (vector < int > &ids)
{
for (int i=1; i<=2 * N; i++)
p[i] = 0;
for (auto it : ids)
p[a[it]] = b[it], p[b[it]] = a[it];
build (1, 1, 2 * N);
for (auto i : ids)
{
ansMi = 4 * N, ansMa = 0, query (1, 1, 2 * N, a[i] + 1, b[i] - 1);
if (ansMi < a[i] || ansMa > b[i])
{
printf ("0\n");
exit (0);
}
}
}
int main ()
{
//freopen ("input", "r", stdin);
//freopen ("output", "w", stdout);
scanf ("%d", &N);
for (int i=1; i<=N; i++)
{
scanf ("%d %d", &a[i], &b[i]);
p[a[i]] = b[i], p[b[i]] = a[i];
pos[a[i]] = pos[b[i]] = i;
}
build (1, 1, 2 * N);
int ans = 1;
for (int i=1; i<=N; i++)
if (ap[i] == 0)
dfs (i, +1), ans = (ans + ans) % mod;
vector < int > v[2];
for (int i=1; i<=N; i++)
v[ap[i] - 1].push_back (i);
check (v[0]), check (v[1]);
printf ("%d\n", ans);
return 0;
}
