#include<bits/stdc++.h>
using namespace std;
long long n,l[100005],r[100005],s;
int main(){
	freopen("usaco_Feb_help.in","r",stdin);
	freopen("usaco_Feb_help.out","w",stdout);
	ios::sync_with_stdio(false);
	cin>>n;
	for(int i=1;i<=n;i++) cin>>l[i]>>r[i];
	for(long long i=1;i<1<<n;i++){
		long long c[n*2+2];
		for(int j=0;j<=n*2+1;j++) c[j]=0;
		for(int j=1;j<=n;j++) if(i&(1<<(j-1))) c[l[j]]++,c[r[j]]--;
		for(int j=1;j<=n*2+1;j++) c[j]+=c[j-1];
		for(int j=1,p=0;j<=n*2+1;j++)
			if(c[j]) p=1;
			else if(p) p=0,s++,s%=1000000007;
	}
	cout<<s;
    return 0;
}