【bzoj2257】墨墨的等式

//在n个数中找k个使得它们的最大公约数最大：从大到小枚举所有数的约数，找到第一个属于超过k个数的约数，即为答案。

program momo;
var n,k,i,v,j,l,a,ans:longint;
    s:array[1..10000000]of longint;
procedure qsort(x,y:longint);
var i,j,mid,t:longint;
begin
 i:=x;j:=y;
 mid:=s[(x+y) div 2];
 repeat
  while s[i]>mid do i:=i+1;
  while s[j]<mid do j:=j-1;
  if i<=j then
   begin
    t:=s[i];s[i]:=s[j];s[j]:=t;
    i:=i+1;j:=j-1;
   end;
 until i>j;
 if i<y then qsort(i,y);
 if x<j then qsort(x,j);
end;
begin
 read(n,k);
 for i:=1 to n do
  begin
   read(v);
   for j:=1 to trunc(sqrt(v)) do
    if v mod j=0 then
     begin
      l:=l+1;
      s[l]:=j;
      if j<>v div j then
       begin
        l:=l+1;
        s[l]:=v div j;
       end;
     end;
  end;
 qsort(1,l);
 a:=1;
 for i:=1 to l-1 do
  begin
   if s[i]=s[i+1] then
    a:=a+1
   else
    a:=1;
   if a>=k then
    begin
     ans:=s[i];
     break;
    end;
  end;
 writeln(ans);
end.