program Project2;

{$APPTYPE CONSOLE}

uses
  SysUtils;
type g = record index,m:integer; end;
var x,a,c:g;
    h:array[1..1000] of g;
    b:array[1..1000,1..2] of integer;
    n,m,i,k,s:integer;
procedure swap(i,j:integer);
var t:g;
begin
t:=h[i];
h[i]:=h[j];
h[j]:=t;
end;

procedure push(x:g);
var k:integer;
begin
inc(n);
h[n]:=x;
k:=n;
while (k>1) and (h[k].m<h[k div 2].m) do
begin
swap(k,k div 2);
k:=k div 2;
end;
end;

function getmin:g;
var k,mini:integer;
minx:g;
begin
getmin:=h[1];
h[1]:=h[n];
dec(n);
k:=1;
while (k<=n) do
begin
mini:=k;
minx:=h[k];
if (2*k<=n) and (h[2*k].m<minx.m) then begin minx:=h[2*k]; mini:=2*k; end;
if (2*k+1<=n) and (h[2*k+1].m<minx.m) then begin minx:=h[2*k+1]; mini:=2*k+1; end;
if mini=k then exit;
swap(mini,k);
k:=mini;
end;
end;
begin
n:=0;  s:=0;
k:=0;
readln(m);
for i:=1 to m do
begin
read(x.m);
x.index:=i;
push(x);
if (i mod 3=0) or (i=m) then
begin
inc(k);
if i=m then begin if i mod 2=1 then begin a:=getmin; b[k,1]:=a.index; s:=s+a.m;end;            end;    end;
if ((i=m) and (i mod 2=0)) or (i mod 3 =0) then begin a:=getmin; c:=getmin; b[k,1]:=a.index; b[k,2]:=c.index;  if a.m>c.m then s:=s+a.m  else s:=s+c.m;         end;
end;
if n=2 then  begin inc(k); a:=getmin; c:=getmin; b[k,1]:=a.index; b[k,2]:=c.index;  if a.m>c.m then s:=s+a.m  else s:=s+c.m;  end;
writeln(s);
for i:=1 to k do
begin
if b[i,2]<>0 then writeln(b[i,1],' ',b[i,2])
             else writeln(b[i,1]);
end;
end.