var a:array[1..10000] of char;
nr,n,i,j:integer;
aux:char;
f,g:text;
ok:boolean;
begin
assign(f,'litere.in');reset(f);
assign(g,'litere.out');rewrite(g);
readln(f,n);
for i:=1 to n do
read(f,a[i]);
ok:=true;
i:=1;
while ok do
begin
if ord(a[i])>ord(a[i+1]) then begin
aux:=a[i];
a[i]:=a[i+1];
a[i+1]:=aux;
inc(nr);
end;
inc(i);
if i=n then i:=1;
for j:=1 to n-1 do
if ord(a[j])>ord(a[j+1]) then begin
ok:=true;
break;
end
else ok:=false;
end;
write(g,nr);
close(f);
close(g);
end.