#include <stdio.h>

int n, m, d[10000];


int e[10000];
void sort(int l, int r) {
	if(l + 1 == r) { return; }
	
	int b = (l + r) / 2;
	sort(l, b);
	sort(b, r);
	
	int ll = l;
	int rr = b;
	while( ! (ll == b && rr == r) ) {
		bool flag;
		if( rr == r ) {
			flag = true;
		} else if( ll == b ) {
			flag = false;
		} else {
			flag = d[ll] <= d[rr];
		}
		
		if(flag) {
			e[ll] = d[ll];
			ll++;
		} else {
			e[rr] = d[rr];
			rr++;
		}
	}
	
	for(int i = l; i < r; i++) {
		d[i] = e[i];
	}
	
	return;
}

int main() {
	scanf("%d%d", &n, &m);
	for(int i = 0; i < m; i++) { scanf("%d", &d[i]); }
	
	sort(0, m);
	
	int min = 30001;
	for(int i = 0; i + (n - 1) < m; i++) {
		int a = d[i], b = d[i + (n - 1)];
		if(a <= 0 && b <= 0) {
			if(-a < min) { min = -a; }
		} else if(0 <= a && 0 <= b) {
			if(b < min) { min = b; } 
		} else {
			int c = -a * 2 + b;
			if(c < min) { min = c; }
			c = -a + b * 2;
			if(c < min) { min = c; }
		}
	}
	
	printf("%d\n", min);
	
	return 0;
}