program goat;
var
  s,p,n,s1,t,min,p1,k:longint;
procedure ini;
var
  i,j:longint;
Begin
  assign(input,'goat.in');
  assign(output,'goat.out');
  reset(input); rewrite(output);
  readln(s,p); k:=0; min:=999999;
End;
procedure go(t,s1,p1:longint);
var
  i,j:longint;
Begin
  if s1<s then begin
    if k>0 then begin
      k:=k-1;
      go(t+1,s1+1,p1-1);
    end
    else begin
      for i:=1 to 3 do begin
        case i of
        1:if p1<>0 then  go(t+1,s1+1,p1-1);
        2:begin
            if p1+2<p then begin
              if p1+2=p then k:=10;
              go(t+1,s1+5,p1+2);
            end;
          end;
        3:begin
            if p1+5<p then begin
              if p1+5=p then k:=10;
              go(t+1,s1+10,p1+5);
            end;
          end;
        end;
      end;
    end;
  end
  else if (s1>=s)and(t<min) then min:=t;
End;
Begin
  ini;
  go(0,0,0);
  writeln(min);
  close
  (input); close(output);
End.