program operatii;
var f:text;
    n,i,r,u,e:longint;

begin
     assign(f,'operatii.in');
     reset(f);
     readln(f,n);
     read(f,r);
     e:=r;
     for i:=2 to n do
     begin
          read(f,u);
          if(u > r) then e:=e+u-r;
          r:=u;
     end;
     close(f);

     assign(f,'operatii.out');
     rewrite(f);
     writeln(f,e);
     close(f);
end.