# correct

x, n = map(int, input().split())

l, r = 0, 2 * 10**9
while r - l > 1:
    m = (l + r) // 2
    sm = m * (m + 1) // 2
    if x > 0:
        if x - sm <= 0:
            r = m
        else:
            l = m
    else:
        if x + sm > 0:
            r = m
        else:
            l = m
k = min(n, l)
d = k * (k + 1) // 2
if n > k:
    if (n - k) % 2:
        d += r + (n - k) // 2
    else:
        d -= (n - k) // 2

if x > 0:
    x -= d
else:
    x += d
print(x)