#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int minimumNumber(int n, char* password) {
    int answer = 0;
    int i;
    int a[4]={0};
    int temp = 0;
    for(i=0;i<n;i++){
        if(*(password+i)>=65 && *(password+i)<=90){
            a[0]++;
        }
        else if(*(password+i)>=97 && *(password+i)<=122){
            a[1]++;
        }
        else if(*(password+i)>=48 && *(password+i)<=57){
            a[2]++;
        }
        else
            a[3]++;
    }
    for(i=0;i<4;i++){
        if(a[i]==0){
            answer++;
        }
    }
    if(n<=3){
        return 6-n;
    }
    if(n==4){
        if(answer <=2){
            return 2;
        }
    }
    if(n == 5){
        if(answer <= 1){
            return 1;
        }
    }
    return answer;
}

int main() {
    int n; 
    scanf("%i", &n);
    char* password = (char *)malloc(512000 * sizeof(char));
    scanf("%s", password);
    int answer = minimumNumber(n, password);
    printf("%d\n", answer);
    return 0;
}