program operatii;
var n,i,a,max,op: longint;
f: text;
begin
     assign(f,'operatii.in');
     reset(f);
     readln(f,n);
     for i:=1 to n do
     begin
         read(f,a);
         if a>max then
              max:=a;
         if a=0 then
         begin
         op:=op+max;
         max:=0;
         end;
     end;
     op:=op+max;
     close(f);
     assign(f,'operatii.out');
     rewrite(f);
     write(f,op);
     close(f);
end.