type vector=array[1..10000] of char;
var n,i,nr,j:longint;
v:vector;
aux:char;
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;
for i:=3 to n+1 do
for j:=i+1 to n+2 do
if v[i]>v[j] then begin
ok:=false;
inc(nr);
aux:=v[i];
v[i]:=v[j];
v[j]:=aux;
end;
writeln(g,nr);
close(f);
close(g);
end.