type itemp = ^item;
     item = record
        cont : integer;
        next : itemp;
     end;
var s,temp:char;
    i,j,n,t,tn,ans,tans:integer;
    sn,tsn:itemp;

procedure additem(var p : itemp;item:integer);{頭から追加}
var q : itemp;
begin
  q := p;
  new(p);
  p^.cont:=item;
  p^.next := q
end;

begin
  readln(n);
  sn:=nil;
  t:=0;
  tn:=1;
  temp:='.';
  for i:=1 to n do begin
    read(s);
    if s=temp then t := t + 1 else begin
      additem(sn,t);
      t := 1;
      tn := tn + 1;
      temp := s
    end;
  end;
  additem(sn,t);
  if temp = '*' then additem(sn,t);
  tn := tn div 2;
  ans:=n;
  for i:=0 to tn do begin
    j := 0;
    tsn := sn;
    tans := 0;
    while tsn<>nil do begin
      j := j + 1;
      if (j <= i*2) and (j mod 2 = 0) then tans := tans + tsn^.cont;
      if (j > i*2) and (j mod 2 = 1) then tans := tans + tsn^.cont;
      tsn:=tsn^.next
    end;
    if tans<ans then ans := tans;
  end;
  writeln(ans);
  {while sn<>nil do begin
    write(sn^.cont);
    sn:=sn^.next
  end;}
end.