program cch(input,output);
var
 s,p,ans:longint;

procedure search(x,y,t:longint);
begin
 if x>=s then
  begin
   if ans>t then ans:=t;
   exit;
  end;
 if t>=ans then exit;
 if y=p then
  begin
   if y>=10 then search(x+10,y-10,t+10)
    else search(x+10,0,t+10);
  end
 else
  begin
   if y<>0 then search(x+1,y-1,t+1);
   if y+2<=p then search(x+5,y+2,t+1);
   if y+5<=p then search(x+10,y+5,t+1);
  end;
end;

begin
 assign(input,'goat.in');
 assign(output,'goat.out');
 reset(input);
 rewrite(output);
 readln(s,p);
 ans:=s;
 search(0,0,0);
 write(ans);
 close(input);
 close(output);
end.