program infoarena_operatii;
type vector=array[1..12] of longint;
var a:vector;
    n,i,j,k,l,k2:longint;

procedure aduna(x:longint);
var retine,pos:longint;
begin
retine:=x;
pos:=1;
repeat
a[pos]:=a[pos]+retine;
retine:=a[pos] div 10;
a[pos]:=a[pos] mod 10;
inc(pos);
until retine=0;
dec(pos);
if pos>l then l:=pos;
end;

begin
assign(input,'operatii.in');
reset(input);
readln(n);
for k:=1 to n do
 begin
  read(i);
  if i>j then begin k2:=i-j; aduna(k2); end;
  j:=i;
 end;
close(input);

assign(output,'operatii.out');
rewrite(output);
for k:=l downto 1 do
  write(a[k]);
close(output);

end.