a[1010],i,n,m,s=1e5,t,p,q;
c(int*a,int*b){t=*a-*b;}
main(){
	for(scanf("%d%d",&n,&m);~scanf("%d",a+q);q++);
	for(qsort(a,q,4,c);i<=m-n;i++){
		p=a[i];q=a[i+n-1];
		t=(abs(p)<abs(q)?abs(q):abs(p));
		p*q<0?t=q*2-p*2-t:0;
		t<s?s=t:0;
	}
	s=!printf("%d",s);
}