import math
x, n = map(int, input().split())
z = abs(2*x - 1)
l = math.isqrt(z)
while z < (l * (l + 1)):
    l -= 1
r = l + 1
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:
    print(x - d)
else:
    print(x + d)