#include <iostream>
#include <map>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> pll;
ll M=1000000007;
int N;
ll X[505],Y[505];
map<ll,ll> S;
map<pll,ll> DP;
ll ans;
unordered_map<ll,ll> R;
ll query(ll k, ll l, ll r, ll a, ll b){
if(b<l or r<a) return 0;
if(a<=l and r<=b) return R[k];
ll m=(l+r)/2;
return (query(2*k,l,m,a,b)+query(2*k+1,m+1,r,a,b))%M;
}
void insert(ll k, ll l, ll r, ll a, ll b){
if(l==r) R[k]=(R[k]+b)%M;
else{
ll m=(l+r)/2;
if(a<=m)
insert(2*k,l,m,a,b);
else
insert(2*k+1,m+1,r,a,b);
R[k]=(R[2*k]+R[2*k+1])%M;
}
}
ll somma(ll a){
return query(1,0,M,a,M-1);
}
void aggiungi(ll a, ll b){
insert(1,0,M,a,b);
}
int main(){
cin>>N;
for(int i=0;i<N;i++)
cin>>X[i]>>Y[i];
for(int i=N-1;i>=0;i--)
for(ll j=X[i];j<=Y[i];j++){
DP[{i,j}]=(somma(j+1)+1)%M;
aggiungi(j,DP[{i,j}]);
ans=(ans+DP[{i,j}])%M;
//cout<<i<<" "<<j<<" "<<DP[{i,j}]<<endl;
}
//for(int i=0;i<10;i++)cout<<i<<" "<<S[i]<<endl;
cout<<ans;
}
/*
3
1 1
2 2
3 3
*/
Compilation message
boat.cpp:13:1: error: 'unordered_map' does not name a type
unordered_map<ll,ll> R;
^~~~~~~~~~~~~
boat.cpp: In function 'll query(ll, ll, ll, ll, ll)':
boat.cpp:18:27: error: 'R' was not declared in this scope
if(a<=l and r<=b) return R[k];
^
boat.cpp: In function 'void insert(ll, ll, ll, ll, ll)':
boat.cpp:27:11: error: 'R' was not declared in this scope
if(l==r) R[k]=(R[k]+b)%M;
^
boat.cpp:35:3: error: 'R' was not declared in this scope
R[k]=(R[2*k]+R[2*k+1])%M;
^
