program asd;
type vect = array [1..10000] of string[1];
var A : vect;
    n,i : integer;
    s : longint;
    f : text;
    x : string[1];
    ok : boolean;
begin
assign(f,'litere.in');
reset(f);
readln(f,n);

for i := 1 to n do
read(f,A[i]);

close(f);
s := 0;
repeat
ok := true;
for i := 1 to n-1 do
if ord(A[i][1])>ord(A[i+1][1]) then begin
                              s := s+1;
                              x := A[i];
                              A[i] := A[i+1];
                              A[i+1] := x;
                              ok := false;
                              end;
until ok;

assign(f,'litere.out');
rewrite(f);
write(f,s);
close(f);
end.