记录编号	48270	评测结果	WWWWWWWWWW
题目名称	奇怪的监狱	最终得分	0
用户昵称	Abel·S	是否通过	未通过
代码语言	Pascal	运行时间	0.003 s
提交时间	2012-11-05 13:23:35	内存使用	0.18 MiB

program cojs_p929;
type
	pri=array[0..1001] of longint;
var
	pos,dis,p:pri;
	n,m,i,j,k,sum:longint;
procedure ass;
begin
	assign(input,'prison.in');
	assign(output,'prison.out');
	reset(input);
	rewrite(output);
end;
procedure cls;
begin
	close(input);
	close(output);
end;
procedure swap(var a,b:longint);
var
	t:longint;
begin
	t:=a;
	a:=b;
	b:=t;
end;
procedure sort1(l,r:longint; var a:pri);
var
	i,j,x:longint;
begin
	i:=l;
	j:=r;
	x:=a[(l+r) div 2];
	repeat
		while a[i]<x do inc(i);
		while x<a[j] do dec(j);
		if i<=j then begin swap(a[i],a[j]); inc(i); dec(j); end;
	until i>j;
	if i<r then sort1(i,r,a);
	if l<j then sort1(l,j,a);
end;
procedure sort2(l,r:longint; var a,b:pri);
var
	i,j,x:longint;
begin
	i:=l;
	j:=r;
	x:=a[(l+r) div 2];
	repeat
		while a[i]<x do inc(i);
		while x<a[j] do dec(j);
		if i<=j then begin swap(a[i],a[j]); swap(b[i],b[j]); inc(i); dec(j); end;
	until i>j;
	if i<r then sort2(i,r,a,b);
	if l<j then sort2(l,j,a,b);
end;
procedure init;
var
	i:longint;
begin
	ass;
	readln(n,m);
	pos[0]:=0;
	fillchar(p,sizeof(p),0);
	p[0]:=2;
	p[n+1]:=2;
	for i:=1 to m do
	begin
		read(pos[i]);
		p[pos[i]]:=1;
	end;
	sort1(1,m,pos);
	for i:=1 to m do
		dis[i]:=pos[i]-pos[i-1]-1;
	dis[m+1]:=n-pos[m];
        pos[m+1]:=n+1;
	sort2(1,m+1,dis,pos);
end;
begin
	init;
	sum:=0;
	for i:=m+1 downto 2 do
	begin
		sum:=sum+(dis[i]*(m+1-i+1));
		p[pos[i]]:=2;
                if pos[i]<m then begin j:=pos[i]+1;
		while p[j]<2 do begin inc(sum,p[j]); inc(j); end; end;
		if pos[i]>0 then begin j:=pos[i]-1;
		while p[j]<2 do begin inc(sum,p[j]); dec(j); end; end;
	end;
	sum:=sum+dis[1]*m;
	writeln(sum);
end.