#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    string s;
    int a;
    int A1=0,A2=0,A3=0,A4=0;
    cin>>a;
    cin>>s;
    for(int i=0;i<a;i++)
    {
        if(s[i]>=65 && s[i]<=90)
            A1++;
        else if(s[i]>=97 && s[i]<=122)
            A2++;
        else if(s[i]>=48 && s[i]<=57)
            A3++;
        else A4++;
            
    }
    int sum=0;
    if(a<6)
    {
         sum=6-a;
    int sum1=0;
    if(A1==0)
        sum1++;
    if(A2==0)
        sum1++;
    if(A3==0)
        sum1++;
    if(A4==0)
        sum1++;
    if(sum1>sum)
        cout<<sum1;
        else cout<<sum;
    }
    else
    {
          if(A1==0)
        sum++;
    if(A2==0)
        sum++;
    if(A3==0)
        sum++;
    if(A4==0)
        sum++;
    cout<<sum;
    }
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}