#include <iostream>
using namespace std;
int main()
{
    int m,n,a[150],sum=0;
    cin>>m>>n;
    for (int i=0;i<=(n-m);i++)
    {
        if ((i+m)%2==1)
        {
            a[i]=m+i;
        }
        else
        {
            continue;
        }
    }
    for (int i=0;i<n;i++)
    {
        sum+=a[i];
    }
    cout<<sum;
    return 0;
}