from collections import deque, defaultdict, Counter
from bisect import bisect_left, bisect_right
from itertools import permutations, combinations
from heapq import heappop, heappush
import math, sys
# input = sys.stdin.readline
_int = lambda x: int(x)-1
MOD = 998244353 #10**9+7
INF = 1<<60
Yes, No = "Yes", "No"

X, N = map(int, input().split())

if X == 0:
    r = 0
else:
    l, r = 0, 10**20
    while r-l>1:
        m = (l+r)//2
        num = (1+m)*m//2
        if X > 0:
            if X-num <= 0: r = m
            else: l = m
        else:
            if X+num > 0: r = m
            else: l = m
if r > N: r = N
if X > 0:
    X -= (1+r)*r//2
else:
    X += (1+r)*r//2

if (N-r)%2:
    r += 1
    if X > 0:
        X -= r
    else:
        X += r
if X > 0:
    X += (N-r)//2
else:
    X -= (N-r)//2
print(X)