int main()
{
     int n,m;
    int result=0;
     scanf("%d %d",&n,&m);
     result=fun(n,m);
     printf("%d",result);
}
int fun(int n,int m){
        int count=0;
        if(m==n){
            count=n;
        }else{
            count=m+fun(n,m-1);

        }
        return count;
    }