import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num1 = scanner.nextInt();
        String str = new String();
        int[] b = new int[num1];
        int[] count = new int[100];
        double avg;
        int max = 0,s = 0;
        int x = 0,m = 0;
            str = scanner.next();
        char a[] = str.toCharArray();
        for (int i = 0; i < num1; i++) {
            if(a[i] == 'V'){
                m++;
                if(i == num1 - 1){
                    if(m < 3){
                        s = m + s;
                    }else if(m >= 3){
                        s = s + 2 * m - 2;
                    }
                }
            }else if(a[i] == 'X'||a[i] == 'T'){
                if(m < 3){
                    s = m + s;
                }else if(m >= 3){
                    s = s + 2 * m - 2;
                }
                m = 0;
                if(a[i] == 'X')s -= 1;
            }

        }
        System.out.println(s);
    }

    public static boolean judge(int i,int j){
        int a,s = 0;
        while(i != 0){
            a = i % 10;
            s = s + a;
            i /= 10;
        }
        if(s == j)return true;
        else return false;
    }

    public static void paiXux(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }public static void paiXu(int[] a,int length){
        int temp;
        for(int i = 0;i < length - 1;i++){
            for(int k = 0;k < length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    } public static void paiXud(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] < a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }

    public static int MAX(int[] a){
        int max = a[0];
        for (int i = 0; i < a.length; i++) {
            if(max < a[i]){
                max = a[i];
            }
        }
        return max;
    }

    public static int MIN(int[] a){
        int min = a[0];
        for (int i = 0; i < a.length; i++) {
            if(min > a[i]){
               min = a[i];
            }
        }
        return min;
    }
    public static int sum(int a){
        int x,s = 0;
        while(a != 0){
            x = a % 10;
            s = s + x;
            a /= 10;
        }
        return s;
    }
    public static boolean isPrime(int a){
        if(a <= 1)return false;
        else
        for(int i = 2;i <= Math.sqrt(a);i++){
            if(a % i == 0)return false;
        }return true;
    }

    public static int qiuYu(int i){
        int a;
        a = i % 10;
        return a;
    }
}

/**************************************************************
	Problem: 2002
	User: admin
	Language: Java
	Result: Accepted
	Time:4280 ms
	Memory:40716 kb
****************************************************************/