Program litere;
 var a:array [1..10005] of char;
     b:array [1..10005] of integer;
     b1:array [1..1 shl 10] of char;
     i,j,k,n:integer;
     nr:longint;
     fi,fo:text;
begin
assign(fi,'litere.in');
 assign(fo,'litere.out');
settextbuf(fi,b1);
reset(fi);
 rewrite(fo);
readln(fi,n);
read(fi,a[1]);
for i:=2 to n do begin
 read(fi,a[i]);
  for k:=i-1 downto 1 do
   if a[k]>a[i] then inc(nr);
  { else if a[k]=a[i] then begin
                            b[i]:=b[i]+b[k];
                            break;
                            end;   }
                 end;
{for i:=1 to n do nr:=nr+b[i];}
write(fo,nr);
close(fo);
end.