var n,k,i,s,x:longint;
begin
     assign(input,'transport.in');
     reset(input);
     assign(output,'transport.out');
     rewrite(output);
     readln(n,k);
     for i:=1 to n do
     begin
          readln(x);
          s:=s+x;
     end;
     writeln(s div k+2);
close(output);
end.