#include <iostream>
using namespace std;
int main() {
long long n,k;
cin>>n>>k;
long long s=0;
for (int i=k; i<=n; i+=k) {
s+=i;
}
cout <<s;
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKaW50IG1haW4oKSB7Cglsb25nIGxvbmcgbixrOwogICAgY2luPj5uPj5rOwogICAgbG9uZyBsb25nIHM9MDsKICAgIGZvciAoaW50IGk9azsgaTw9bjsgaSs9aykgewogICAgICAgIHMrPWk7CiAgICB9CiAgICBjb3V0IDw8czsKCXJldHVybiAwOwp9