H, W = map(int, input().split())
D = abs(W)

if H == 0 or D == 0:
    print(0)
else:
    if D <= H:
        ans = (H - D) + (D * (D + 1)) // 2
    else:
        ans = H * (D - H) + H * (H + 1) // 2
    print(ans)