import java.util.Scanner; public class Mugs { static int mugs; public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); sc.nextLine(); String line = sc.nextLine(); int poz = 0; int poc = 2; rec(poz, poc, line); System.out.println(mugs); /* for (int i = 0; i < line.length(); i++) { if (occ.containsKey(line.charAt(i))) { occ.put(line.charAt(i), occ.get(line.charAt(i)) + 1); } else { occ.put(line.charAt(i), 1); } }*/ /* int mugs = 0; for (int i = 0; i < line.length(); i++) { for (int r = i; r < line.length(); r++) { mugs = Math.max(mugs, getFunc(line.substring(r))); } } System.out.println(mugs); */ } public static void rec(int poz, int poc, String line) { if(poz < line.length()-1) { if(poc >= line.length()+1) { poz++; rec(poz, poz+2, line); } else { int mugsPom = getFunc(line.substring(poz, poc)); if(mugsPom != -1 && mugsPom > mugs) { mugs = Math.max(mugs, mugsPom); } poc++; rec(poz, poc, line); } } } public static int getFunc(String line) { // System.out.println(line); if(line.length() % 2 == 0) { int count = 0; for (int i = 0; i < line.length(); i++) { char c = line.charAt(i); if(line.substring(i+1).contains(String.valueOf(c)) && c != '*') { line = line.replaceFirst(String.valueOf(c), "*"); line = line.replaceFirst(String.valueOf(c), "*"); count++; } } if(count == line.length()/2) { return line.length(); } else { return -1; } } else { int count = 0; int contain = 0; for (int i = 0; i < line.length(); i++) { char c = line.charAt(i); if(line.substring(i+1).contains(String.valueOf(c)) && c != '*') { line = line.replaceFirst(String.valueOf(c), "*"); line = line.replaceFirst(String.valueOf(c), "*"); count++; } else { if(c != '*') { if(contain == 0) { contain = 1; } else { contain = 2; } } } } if(count == line.length()/2 && (contain == 1 || contain == 0)) { return line.length(); } else { return -1; } } } }