// yukicoder: 370 道路の掃除
// 2019.6.9 bal4u

#include <stdio.h>
#include <stdlib.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif
int in()   // 整数の入力（負数対応）
{
	int n = 0, c = gc();
	if (c == '-') {	c = gc();
		do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
		return -n;
	}
	do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

#define INF 0x11111111
int a[1002], b[1002], as, bs;
int cmp(const void *a, const void *b) { return *(int *)a - *(int *)b; }

int main()
{
	int i, lim, N, M, d, t, ans;
	
	N = in(), M = in();
	as = bs = 0;
	while (M--) {
		d = in();
		if (d == 0) N--;
		else if (d > 0) a[as++] = d;
		else            b[bs++] = -d;
	}
	if (N == 0) { puts("0"); return 0; }
	
	qsort(a, as, sizeof(int), cmp);
	qsort(b, bs, sizeof(int), cmp);
	
	ans = INF;
	if (bs >= N) ans = b[N-1], bs = N;
	if (as >= N && a[N-1] < ans) ans = a[N-1];
	lim = 0; if (as < N-1) lim = N-as-1;
	for (i = bs-1; i >= lim; i--) {
		d = b[i];
		if (a[N-i-2] < d) d = a[N-i-2];
		if ((t = d + b[i] + a[N-i-2]) < ans) ans = t;
	}
	printf("%d\n", ans);
	return 0;
}