#include <bits/stdc++.h>

using namespace std;

int minimumNumber(int n, string s) 
{
    // Return the minimum number of characters to make the password strong
    int n1=0,u=0,l=0,s1=0;
    for(int i=0;i<n;i++)
    {
        if(s[i]>='a' && s[i]<='z')
            l=1;
        else if(s[i]>='0' && s[i]<='9')
            n1=1;
        else if(s[i]>='A' && s[i]<='Z')
            u=1;
        else 
            s1=1;   
    }
    int x=4-(n1+u+l+s1);

    if(n<6)
    {
        int y=6-n;
        if(x>y)
            return x;
        else 
            return y;
        
    }
    else 
        return x;
    
}

int main() {
    int n;
    cin >> n;
    string password;
    cin >> password;
    int answer = minimumNumber(n, password);
    cout << answer << endl;
    return 0;
}