#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl;
#define show4(x,y) for(auto it:y) cout << it << " "; cout << #x << endl;
typedef pair<int,int>pii;
typedef pair<pii,int>pi2;
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const int mod=1e9+7;
int f(int a, int b){
if(a==1||b==0) return 1;
if(b==1) return a;
int hold=f((a*a)%mod,b/2);
if(b%2) hold=(hold*a)%mod;
return hold;
}
int fac[1005];
int memo[505][505];
int f2(int n, int k){
if(n==0) return 0;
if(memo[n][k]!=-1) return memo[n][k];
int hold=fac[n+k];
int hold2=f(fac[n-1],mod-2);
int hold3=f(fac[k+1],mod-2);
hold=(hold*hold2)%mod;
hold=(hold*hold3)%mod;
return memo[n][k]=hold;
}
void solve(){
int n;
cin >> n;
pii arr[n];
vector<int>v;
for(int x=0;x<n;x++){
cin >> arr[x].first >> arr[x].second;
v.push_back(arr[x].first);
v.push_back(arr[x].second+1);
}
sort(v.begin(),v.end());
v.resize(unique(v.begin(),v.end())-v.begin());
vector<int>storage[2*n+5];
int len[2*n+5];
for(int x=0;x<(int)v.size()-1;x++){
len[x]=v[x+1]-v[x];
}
for(int x=0;x<n;x++){
int cur=arr[x].first;
while(cur<=arr[x].second){
int index=upper_bound(v.begin(),v.end(),cur)-v.begin();
storage[index-1].push_back(x);
cur=v[index];
}
}
fac[0]=1;
for(int x=1;x<1000;x++){
fac[x]=(fac[x-1]*x)%mod;
}
memset(memo,-1,sizeof(memo));
int ans=0;
int cnt[n];
memset(cnt,0,sizeof(cnt));
for(int x=0;x<(int)v.size();x++){
int prefix[n];
memset(prefix,0,sizeof(prefix));
prefix[0]=cnt[0];
for(int y=1;y<n;y++){
prefix[y]=(cnt[y]+prefix[y-1])%mod;
}
int sz=storage[x].size();
int add[n];
memset(add,0,sizeof(add));
for(int y=0;y<sz;y++){
int counter=0;
for(int i=0;i<=y;i++){
int val;
if(y==i) val=len[x];
else val=f2(len[x]-1,y-i);
int multi=0;
if(storage[x][i]>0) multi=prefix[storage[x][i]-1];
int hold=(multi*val)%mod;
counter=(counter+hold)%mod;
}
int hold=f2(len[x],y);
counter=(counter+hold)%mod;
add[storage[x][y]]=(add[storage[x][y]]+counter)%mod;
ans=(ans+counter)%mod;
}
for(int y=0;y<n;y++){
cnt[y]=(cnt[y]+add[y])%mod;
}
}
cout << ans;
}
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0);
//freopen("in.txt","r",stdin);
//freopen("in.txt","w",stdout);
int t=1;
//cin >> t;
while(t--){
solve();
}
}
