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

        assign(g,'operatii.out');
        rewrite(g);
        s:=s+max;
        write(g,s);
        close(g);
end.