ProcedurProgramavimas_1.13

#include <iostream>
#include <iomanip>

using namespace std;
int main()
{
    long double sum=0;
    long double a, n;
    cin>>a;
    cin>>n;

    for(int i = a-1; i < n; i++ )
    {
        sum+=a;
        a+=1;
    }

    cout<<fixed<<setprecision(0)<<sum<<endl;

    return 0;
}