type vector=array[1..10000] of char;
var n,i,nr,j:longint;
v:vector;
ok:boolean;
f,g:text;
begin
assign(f,'litere.in');reset(f);
assign(g,'litere.out');rewrite(g);
read(f,n);
for i:=1 to n+2 do
read(f,v[i]);
nr:=0;
i:=3;
while i<=n+2 do begin
j:=i+1;
while j<=n+2 do begin
if v[i]>v[j] then inc(nr);
inc(nr);
end;
inc(i);
end;
writeln(g,nr);
close(f);
close(g);
end.