//Power Of Ninja Go
#include <bits/stdc++.h>
//#ifdef atom #else #endif
using namespace std;
typedef long long ll; typedef pair<int, int> ii; typedef vector<int> vi; typedef vector< ii > vii;
#define X first
#define Y second
#define pb push_back
const int maxn = 1e6+5;
int n;
int st[23][2*maxn];
int lend[8*maxn];
int Rend[8*maxn];
int toy[2*maxn];
int tox[2*maxn];
int p[2*maxn];
vector<int> vals;
int cc;
vector<int> comps[2*maxn];
vector<int> adj[2*maxn];
queue< ii > q;
int col[2*maxn];
const int md = 1e9+7;
void init(int p = 1, int L = 1, int R = 2*n)
{
lend[p] = L, Rend[p] = L-1;
if(L == R) return;
init(2*p, L, (L+R)/2); init(2*p+1, (L+R)/2+1, R);
}
void add(int x, int val, int p = 1, int dep = 1, int L = 1, int R = 2*n)
{
Rend[p]++;
st[dep][Rend[p]] = val;
if(L == R) return;
int M = (L+R)/2;
if(x<= M) add(x, val, 2*p, 1+dep, L, M);
else add(x, val, 2*p+1, 1+dep, M+1, R);
}
void get(int i, int j, int key, int p = 1, int dep = 1, int L = 1, int R = 2*n)
{
if(i> R || j< L) return;
if(i<= L && R<= j)
{
while(lend[p]<= Rend[p] && st[dep][lend[p]]< key)
{
vals.pb(st[dep][lend[p]]);
lend[p]++;
}
return;
}
int M = (L+R)/2;
get(i, j, key, 2*p, dep+1, L, M); get(i, j, key, 2*p+1, dep+1, M+1, R);
}
int findset(int x)
{
if(x == p[x]) return x;
return p[x] = findset(p[x]);
}
void unionset(int x, int y)
{
int a = findset(x), b = findset(y);
if(a == b) return;
cc--;
p[a] = b;
}
int main()
{
scanf("%d", &n);
init(); cc = n;
for(int i = 1; i<= 2*n; i++) p[i] = i;
for(int i = 1; i<= n; i++)
{
int x, y; scanf("%d %d", &x, &y);
toy[x] = y; tox[y] = x;
}
for(int i = 1; i<= 2*n; i++)
{
if(!toy[i]) continue;
get(i, toy[i], i);
while(!vals.empty())
{
int x = vals.back(); vals.pop_back();
//printf("union %d to %d\n", x, i);
unionset(x, i);
adj[x].pb(i); adj[i].pb(x);
}
add(toy[i], i);
}
init();
for(int i = 2*n; i; i--)
{
if(!tox[i]) continue;
get(tox[i], i, -i);
while(!vals.empty())
{
int x = -vals.back(); vals.pop_back();
//printf("union %d to %d\n", tox[x], tox[i]);
unionset(tox[x], tox[i]);
adj[tox[x]].pb(tox[i]); adj[tox[i]].pb(tox[x]);
}
add(tox[i], -i);
}
int ans = 1;
for(int i = 1; i<= 2*maxn; i++)
{
if(!toy[i]) continue;
if(col[i]) continue;
ans = (2LL*ans)%md;
q.push(ii(i, 1));
while(!q.empty())
{
ii z = q.front(); q.pop();
//printf("(%d, %d)\n", z.X, z.Y);
if(col[z.X])
{
if(col[z.X] != z.Y)
{
ans = 0; break;
}
continue;
}
col[z.X] = z.Y;
for(auto v : adj[z.X])
{
q.push(ii(v, -z.Y));
}
}
}
printf("%d\n", ans);
}
