#include <bits/stdc++.h>
#define maxn 505
#define f first
#define s second
#define pii pair<int,int>
#define mod (long long)(1e9 + 7)
using namespace std;
int n;
int a[maxn][2];
pair<pii,int> d[2*maxn];
int pl[maxn];
int pr[maxn];
long long dp[2*maxn][maxn];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cin>>n;
for(int i=1;i<=n;i++)
{
cin>>a[i][0]>>a[i][1];
d[2*i-1]={{a[i][0],0},i};
d[2*i]={{a[i][1],1},i};
}
sort(d+1,d+2*n+1);
for(int i=1;i<=2*n;i++)
{
if(d[i].f.s==0) pl[ d[i].s ]=i;
else pr[ d[i].s ]=i;
}
for(int i=1;i<=n;i++)dp[0][i]=0;
dp[0][0]=1;
dp[0][d[1].s]=1;
for(int i=1;i<=2*n-1;i++)
{
dp[i][0]=1;
for(int j=1;j<=n;j++)
{
dp[i][j]=dp[i-1][j];
int dod=0;
if(d[i].f.f==d[i+1].f.f)continue;
if(pl[j]==i+1)dod=1;
else if(pl[j]<=i && i+1<=pr[j])dod=d[i+1].f.f-d[i].f.f;
else continue;
//cout<<i<<" "<<j<<" "<<dod<<endl;
for(int k=0;k<j;k++)
{
dp[i][j]+=dp[i-1][k]*dod;
dp[i][j]%=mod;
}
}
}
long long sol=0;
for(int i=1;i<=n;i++)
{
sol+=dp[2*n-1][i];
sol%=mod;
}
/*for(int i=1;i<=2*n;i++)cout<<d[i].f.f<<" "<<d[i].f.s<<" "<<d[i].s<<endl;cout<<endl;
for(int i=1;i<=n;i++)cout<<i<<" "<<pl[i]<<" "<<pr[i]<<endl;cout<<endl;
for(int i=0;i<=2*n-1;i++)
{
cout<<i<<" ";
for(int j=0;j<=n;j++)cout<<dp[i][j]<<" ";
cout<<endl;
}*/
cout<<sol<<endl;
return 0;
}
