#include <bits/stdc++.h>
using namespace std;
const int NM = 2e6, inf = 1e9+7, MOD = 1e9+7;
int N, r[NM+5], cnt = 0, ans = 1;
int suml[NM+5], sumr[NM+5], mn[NM+5], mn2[NM+5];
void update_sum(int sum[NM+5], int x){
while (x <= NM){
sum[x]++;
x += x & (-x);
}
}
void update_mn(int mn[NM+5], int x, int val){
while (x <= NM){
mn[x] = min(mn[x], val);
x += x & (-x);
}
}
int get_sum(int sum[NM+5], int x){
int res = 0;
while (x > 0){
res += sum[x];
x -= x & (-x);
}
return res;
}
int get_mn(int mn[NM+5], int x){
int res = +inf;
while (x > 0){
res = min(res, mn[x]);
x -= x & (-x);
}
return res;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> N;
for (int i = 1; i <= N; i++){
int x, y; cin >> x >> y;
r[x] = y;
}
for (int i = 1; i <= NM; i++) mn[i] = mn2[i] = +inf;
for (int i = 2*N; i >= 1; i--){
if (r[i] == 0) continue;
cnt += get_sum(suml, r[i])-get_sum(sumr, r[i]);
update_sum(suml, i);
update_sum(sumr, r[i]);
if (get_mn(mn2, 2*N-(r[i]+1)+1) <= r[i]){
cout << 0;
return 0;
}
int tmp = get_mn(mn, 2*N-(r[i]+1)+1);
if (tmp <= r[i]){
update_mn(mn2, 2*N-r[i]+1, tmp);
}
update_mn(mn, 2*N-r[i]+1, i);
}
assert(cnt < N);
for (int i = 1; i <= N-cnt; i++) ans = ans*2%MOD;
cout << ans;
return 0;
}
