program operatii;
var op: int64;
n,a,b,i:longint;
f: text;
begin
     assign(f,'operatii.in');
     reset(f);
     readln(f,n);
     for i:=1 to n do
     begin
          read(f,a);
          if a>b then op:=op+a-b;
          b:=a;
     end;
     close(f);
     assign(f,'operatii.out');
     rewrite(f);
     write(f,op);
     close(f);
end.