resturi2

#include<iostream>
using namespace std;
int main()
{
    int n, k;
    long long suma, p=0;
    cin>>n>>k;
    if(n%k==0)
    {
        p=n/k;
    }
    else
        {
            p=(n/k)+1;
        }
    suma=p*((k-1)*k/2);
    cout<<suma;
    return 0;
}