#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
#define all(v) v.begin(),v.end()
#define pb push_back
#define sz(v) (int)v.size()
const int MOD = 1e9+7;
const int64_t INF = 1e18;
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie();
//If you hack my code , You are gay;
int n;
cin>>n;
vector<int> L(n),R(n);
vector<int> v={0};
for(int i=0;i<n;i++){
cin>>L[i]>>R[i];
for(int j=L[i];j<=R[i];j++){
v.push_back(j);
}
}
sort(all(v));
v.erase(unique(all(v)),v.end());
for(int i=0;i<n;i++){
L[i] = lower_bound(all(v),L[i])-v.begin();
R[i] = lower_bound(all(v),R[i])-v.begin();
//cout<<L[i]<<" "<<R[i]<<"\n";
}
vector<vector<int>> dp(n+1,vector<int>(sz(v)+1,0)),sum(n+1,vector<int>(sz(v)+1,0));
dp[0][0]=1;
for(int i=0;i<sz(v);i++) sum[0][i] = 1;
for(int i=1;i<=n;i++){
for(int j=L[i-1];j<=R[i-1];j++){
dp[i][j] = (dp[i][j] + sum[i-1][j-1])%MOD;
}
sum[i][0] = 1;
for(int j=1;j<sz(v);j++){
sum[i][j] = (dp[i][j] + sum[i-1][j] + sum[i][j-1] - sum[i-1][j-1])%MOD;
}
}
cout<<(sum[n][sz(v)-1]-1+MOD)%MOD;
return 0;
}
