#include <bits/stdc++.h>
#define FAST ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);cerr.tie(0)
#define mp make_pair
#define xx first
#define yy second
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define all(x) x.begin(),x.end()
#define ff(i,a,b) for (int i = a; i < b; i++)
#define fff(i,a,b) for (int i = a; i <= b; i++)
#define bff(i,a,b) for (int i = b-1; i >= a; i--)
#define bfff(i,a,b) for (int i = b; i >= a; i--)
using namespace std;
long double typedef ld;
unsigned int typedef ui;
long long int typedef li;
pair<int,int> typedef pii;
pair<li,li> typedef pli;
pair<ld,ld> typedef pld;
vector<vector<int>> typedef graph;
unsigned long long int typedef ull;
//const int mod = 998244353;
const int mod = 1000000007;
//Note to self: Check for overflow
int a[505],b[505];
int dp[1069];
int main()
{
FAST;
int n; cin>>n;
fff(i,1,n) cin>>a[i]>>b[i];
vector<int> kords;
kords.pb(0);
kords.pb(1);
kords.pb(mod);
fff(i,1,n) kords.pb(a[i]);
fff(i,1,n) kords.pb(b[i]+1);
sort(all(kords));
kords.erase(unique(all(kords)),kords.end());
dp[0]=1;
fff(i,1,n)
{
int tsum=0;
ff(x,0,(int)kords.size())
{
int stari=dp[x];
if (a[i]<=kords[x] && kords[x]<=b[i]){
(dp[x]+=(li)(kords[x+1]-kords[x])*tsum%mod)%=mod;
}
(tsum+=stari)%=mod;
}
//ff(x,0,(int)kords.size()) cout<<dp[x]<<" "; cout<<endl;
}
int ans=0;
ff(x,1,(int)kords.size()) (ans+=dp[x])%=mod;
cout<<ans<<"\n";
}
//Note to self: Check for overflow
