#include<stdio.h>
#include<vector>
#include<algorithm>
#include<set>
#include<queue>
using namespace std;
#define SIZE (1<<21)
int toz[SIZE];
class segtree
{
public:
int seg1[22][SIZE];
int seg2[22][SIZE];
int low[SIZE*2],u1[SIZE*2],u2[SIZE*2];
int x[SIZE * 2];
int pt;
void init()
{
for(int i=0;i<SIZE;i++)low[i+SIZE]=u1[i+SIZE]=u2[i+SIZE]=i;
for(int i=SIZE-1;i>=1;i--)low[i]=low[i*2],u1[i]=u1[i*2],u2[i]=u2[i*2];
}
void add1(int beg, int end)
{
int node = 1;
int lb = 0, ub = SIZE - 1;
int dep=0;
for (;;)
{
seg1[dep][u1[node]++]=end;
if (lb == ub)break;
node *= 2;
dep++;
if (beg <= (lb + ub) / 2)ub = (lb + ub) / 2;
else lb = (lb + ub) / 2 + 1, node++;
}
}
void add2(int beg,int end)
{
int node = 1;
int lb = 0, ub = SIZE - 1;
int dep=0;
for (;;)
{
seg2[dep][u2[node]++]=beg;
if (lb == ub)break;
node *= 2;
dep++;
if (end <= (lb + ub) / 2)ub = (lb + ub) / 2;
else lb = (lb + ub) / 2 + 1, node++;
}
}
void get(int beg, int end, int node, int lb, int ub, int dep)
{
if (end < lb || ub < beg)return;
if (beg <= lb&&ub <= end)
{
for (;;)
{
if(low[node]==u1[node])break;
int z=seg1[dep][u1[node]-1];
if(z<=end)break;
x[pt++] = toz[z];
u1[node]--;
}
for (;;)
{
if(low[node]==u2[node])break;
int z=seg2[dep][u2[node]-1];
if(z>=beg)break;
x[pt++] = toz[z];
u2[node]--;
}
return;
}
get(beg, end, node * 2, lb, (lb + ub) / 2, dep+1);
get(beg, end, node * 2 + 1, (lb + ub) / 2 + 1, ub,dep+1);
}
};
segtree tree;
int a[1000000], b[1000000];
int col[2000000];
typedef pair<int, int>pii;
int main()
{
int num;
scanf("%d", &num);
for (int i = 0; i < num; i++)scanf("%d%d", &a[i], &b[i]), a[i]--, b[i]--, toz[a[i]] = toz[b[i]] = i;
tree.init();
for(int i=0;i<num+num;i++)if(b[toz[i]]==i)tree.add1(a[toz[i]],b[toz[i]]);
for(int i=num+num-1;i>=0;i--)if(a[toz[i]]==i)tree.add2(a[toz[i]],b[toz[i]]);
int ans = 1;
for (int i = 0; i < num; i++)
{
if (col[i] == 0)
{
ans = ans * 2 % 1000000007;
queue<pii>que;
que.push(make_pair(i, 1));
for (;;)
{
if (que.empty())break;
pii z = que.front();
que.pop();
if (col[z.first] != 0)
{
if (col[z.first] != z.second)
{
printf("0\n");
return 0;
}
continue;
}
col[z.first] = z.second;
tree.pt = 0;
tree.get(a[z.first], b[z.first], 1, 0, SIZE - 1, 0);
for (int j = 0; j < tree.pt; j++)que.push(make_pair(tree.x[j], -z.second));
}
}
}
printf("%d\n",ans);
}
