var n,i,s,a1,a2:longint;
    f,g:text;


Begin
     assign(f,'operatii.in');
     assign(g,'operatii.out');
     reset(f);
              s:=0;
              readln(f,n);
              read(f,a1);
              for i:=2 to n do
              begin
                   a2:=a1;
                   read(f,a1);
                   if a1-a2>0 then
                   begin
                        s:=s+a1-a2
                   end;
              end;

     close(f);

     rewrite(g);
                writeln(g,s);
     close(g);
End.