var a:array [0..1000000] of integer;
  i,n,nr:longint;
  f,t:text;

begin
  assign(f,'operatii.in');
  assign(t,'operatii.out');
  reset(f);
  rewrite(t);
  readln(f,n);
  nr:=0;
  for i:=1 to n do
    begin
    read(f,a[i]);
    if a[i]>a[i-1] then nr:=nr+(a[i]-a[i-1]);
    end;
  writeln(t,nr);
  close(f);
  close(t);
end.