#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) {
    //char count[256]={0};
    int num=0,upper=0,lower=0,sym=0,count=0;
    for(int i=0;i<n;i++)
    {
        if(password[i]>='a'&&password[i]<='z')
        {if(lower==0)count++;lower++;}
        else if(password[i]>='A'&&password[i]<='Z')
        {if(upper==0)count++;upper++;}
        else if((password[i]>='0'&&password[i]<='9'))
        {if(num==0)count++;num++;}
        else
        {if(sym==0)count++;sym++;}
            
            }
    if(n>=6)
    {
        if(lower&&upper&&num&&sym)
            return 0;
        else if(lower&&upper&&num||lower&&upper&&sym||lower&&sym&&num||upper&&num&&sym)
            return 1;
        else if(lower&&upper||upper&&num||num&&sym||lower&&num||lower&&sym||upper&&sym)
            return 2;
        else if(lower||upper||num||sym)
            return 3;
        else
            return 4;
            
    }
    else
    {
        int d=6-n;
        if(d>=3)
            return d;
       else if(lower&&upper&&num&&sym)
            return d;
        else if(count==3||count==4)
            return d;
        else if(count==2&&d>=2)
            return d;
        else if(count==2&&d==1)
            return d+1;
        else if(count==2&&d==0)
            return d+2;
        else if(count==1&&d>=3)
            return d;
        else if(count==1&&d==2)
            return d+1;
        else if(count==1&&d==1)
            return d+2;
        
    }
    return 0;
    // Return the minimum number of characters to make the password strong
}

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;
}