package main

import . "fmt"

func main() {
	check()
	var x, n int64
	Scan(&x, &n)
	Println(solve(x, n))
}

func check() {
	for x := int64(-1000); x <= 1000; x++ {
		for n := int64(1); n <= 1000; n++ {
			br := bruteforce(x, n)
			sr := solve(x, n)
			if br != sr {
				panic(Errorf("x=%d,n=%d,br=%d,sr=%d",x,n,br,sr))
			}
		}
	}
}

func bruteforce(x, n int64) int64 {
	for i := int64(1); i <= n; i++ {
		if x <= 0 {
			x += i
		} else {
			x -= i
		}
	}
	return x
}

func init() {
	if res := bruteforce(2, 3); res != 2 {
		panic(Errorf("x=2,n=3,ans=2,res=%d",res))
	}
	if res := bruteforce(10, 3); res != 4 {
		panic(Errorf("x=10,n=3,ans=4,res=%d",res))
	}
}

func solve(x, n int64) int64 {
	ax := x
	if ax < 0 {
		ax = -ax
	}
	upper := int64(2e9)
	lower := int64(0)
	for lower + 1 < upper {
		v := (upper+lower)/2
		sum := v*(v+1)/2
		if sum < ax {
			lower = v
		} else {
			upper = v
		}
	}
	if upper > n {
		upper = n
	}
	if x <= 0 {
		x += upper*(upper+1)/2
	} else {
		x -= upper*(upper+1)/2 
	}
	if upper == n {
		return x
	}
	if x <= 0 {
		if (n-upper)%2 == 0 {
			x -= (n-upper)/2
		} else {
			x += upper+1 + (n-upper)/2
		}
	} else {
		if (n-upper)%2 == 0 {
			x += (n-upper)/2
		} else {
			x -= upper+1 + (n-upper)/2
		}
	}
	return x
}