#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* s) {
    // Return the minimum number of characters to make the password strong

        int a,b,c,d;
        a=b=c=d=0;
        for(int i=0;i<n;i++)
        {
            if(*(s+i)>='0' && *(s+i)<='9')
            {
                a=1;
            }
            else if(*(s+i)>='a' && *(s+i)<='z')
            {
                b=1;
            }
            else if(*(s+i)>='A' && *(s+i)<='Z')
            {
                c=1;
            }
            else
            {
                d=1;
            }
            if(a+b+c+d == 4 && n>=6)
            {
                return 0;
            }
        }
        int val = a+b+c+d;
            
        if(n<6)
        {
            if((6-n)>4-val)
            {
                return (6-n);
            }
            else
            {
                return(4-val);
            }
        }
        else
        {
            return(4-(a+b+c+d));
        }
        
    
}

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;
}