var
   n,i:longint;
   a:array[1..100000] of longint;
   f,g:text;
function rez:longint;
var
   i,s,max:longint;

 begin

  s:=0;
  max:=0;

  for i:=  1 to n do begin

   if a[i]>max then
     max:=a[i]

     else if a[i]=0 then
       begin
        s:=s+max;
        max:=0;
       end;
   end;

  s:=s+max;
  rez:=s;

 end;

begin

 assign(f,'operatii.in');
 reset(f);

 readln(f,n);
 for i:=1 to n do
  read(f,a[i]);

 close(f);

 assign(g,'operatii.out');
 rewrite(g);
 writeln(g,rez);

 close(g);

end.