#include <bits/stdc++.h>
using namespace std;
int const MOD=1e9+7;
int const MAX=505;
int n;
vector<int>pos;
int a[MAX],b[MAX];
int comb[MAX][MAX];
int inv[MAX];
int combi[MAX]; /// C len,i
int add[2*MAX][MAX];
/// nr de moduri sa adaugam in al i-lea interval
/// j puncte (unde adaugam un subset de la 1 la j-1
/// si pe j sigur)
int dp[2*MAX][MAX];
/// nr de moduri sa adaugam in primele i intervale
/// puncte pana la j (pe j il adaugam sigur)
bool inclus[MAX];
int bin_exp(int base,int exp){
int rez=1;
while(exp){
if(exp&1)
rez=1LL*rez*base%MOD;
base=1LL*base*base%MOD;
exp/=2;
}
return rez;
}
void get_comb(){
comb[0][0]=1;
int i,j;
for(i=1;i<=n;++i){
comb[i][0]=1;
for(j=1;j<=i;++j)
comb[i][j]=(comb[i-1][j]+comb[i-1][j-1])%MOD;
}
for(i=1;i<=n;++i)
inv[i]=bin_exp(i,MOD-2);
}
void read(){
cin>>n;
int i;
for(i=1;i<=n;++i){
cin>>a[i]>>b[i];
++b[i];
pos.push_back(a[i]);
pos.push_back(b[i]);
}
sort(pos.begin(),pos.end());
auto it=unique(pos.begin(),pos.end());
pos.resize(distance(pos.begin(),it));
}
void get_add(){
int intv,i,j;
for(intv=0;intv<(int)pos.size()-1;++intv){
int len=pos[intv+1]-pos[intv];
int rez=1;
for(i=1;i<=n && i<=len;++i){
rez=1LL*rez*(len-i+1)%MOD;
rez=1LL*rez*inv[i]%MOD;
combi[i]=rez;
}
for(i=1;i<=n;++i)
for(j=0;j<i && j<len;++j)
add[intv][i]=(add[intv][i]+1LL*comb[i-1][j]*combi[j+1]%MOD)%MOD;
}
}
void get_dp(){
int intv,i,j;
for(intv=0;intv<(int)pos.size()-1;++intv){
for(i=1;i<=n;++i)
inclus[i]=(a[i]<=pos[intv] && pos[intv+1]<=b[i]);
dp[intv][0]=1;
if(intv){
for(i=1;i<=n;++i)
dp[intv][i]=dp[intv-1][i];
for(i=1;i<=n;++i)
if(inclus[i]){
int cnt=1;
for(j=i-1;j>=0;--j){
dp[intv][i]=(dp[intv][i]+1LL*dp[intv-1][j]*add[intv][cnt]%MOD)%MOD;
cnt+=inclus[j];
}
}
}
else{
int cnt=0;
for(i=1;i<=n;++i)
if(inclus[i]){
++cnt;
dp[intv][i]=add[intv][cnt];
}
}
}
}
int get_ans(){
int sum=0;
int i;
for(i=1;i<=n;++i)
sum=(sum+dp[(int)pos.size()-2][i])%MOD;
return sum;
}
int main()
{
read();
get_comb();
get_add();
get_dp();
cout<<get_ans();
return 0;
}
