import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        ArrayList<Character> list = new ArrayList<>();
        int ans = 0;
        for (char c : sc.next().toCharArray()) {
            if (list.size() == 0) {
                list.add(c);
            } else if (list.size() == 1) {
                if (list.get(0) != c) {
                    list.add(c);
                }
            } else {
                if (list.get(list.size() - 1) != c) {
                    if (list.get(list.size() - 2) == c) {
                        list.remove(list.size() - 1);
                        ans++;
                    } else {
                        list.add(c);
                    }
                }
            }
        }
        int[] counts = new int[3];
        for (char c : list) {
            if (c == 'R') {
                counts[0]++;
            } else if (c == 'G') {
                counts[1]++;
            } else {
                counts[2]++;
            }
        }
        Arrays.sort(counts);
        ans += counts[0] + counts[1] + 1;
        System.out.println(ans);
    }
}

class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}