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

        assign(g,'operatii.out');
        rewrite(g);
        write(g,s);
        close(g);
end.