#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* p) {
    // Return the minimum number of characters to make the password strong
    int i,count=0,in=0,up=0,lo=0,sp=0;
    for(i=0;i<n;i++)
    {
        if(p[i]>='0'&&p[i]<='9')
            in=1;
        else if(p[i]>='a'&&p[i]<='z')
            lo=1;
        else if(p[i]>='A'&&p[i]<='Z')
            up=1;
        else
            sp=1;
    }
    int s=in+up+lo+sp;
    if(n<=3)
    {
        return 6-n;
    }
    else if(n==4)
    {
        if(s>=2)
        {
        return 2;
        }
        else
            return 3;
    }
   else if(n==5)
   {
       if(s>=3)
              return 1;
       else return 4-s;
   }
   else
        return 4-s;
}

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;
}