#include <bits/stdc++.h>
using namespace std;
int main(void){
    long long H, W; cin >> H >> W;
    if (!W || !H) {
        cout << 0 << endl;
        return 0;
    }
    W = W < 0 ? -W : W;
    cout << H + max(0LL, (W-H)) * H + (W-H >= 0 ? H*(H-1)/2 : W*(W-1)/2)  << endl;
}