include[HTML_REMOVED]

include[HTML_REMOVED]

using namespace std;
int sum(int l,int r){
int c=0;
for(int i=l;i<=r;i++){
c+=i;
}
return c;
}
int main(){
int l,r;
cin>>l>>r;
cout<<sum(l,r)<<endl;
return 0;
}