#include <bits/stdc++.h>

using namespace std;

int minimumNumber(int n, string p) {
    // Return the minimum number of characters to make the password strong
    int l=0,u=0,s=0,d=0;
    for(int i=0;i<n;i++){
        if(p[i]>=48 && p[i]<=57) d++;
        else if(p[i]>=65 && p[i]<=90) u++;
        else if(p[i]>=97 && p[i]<=122) l++;
        else s++;
    }
    int add=0;
    
    if(n>=6){
        if(!l) add++;
        if(!s) add++;
        if(!u) add++;
        if(!d) add++;
        return add;
    }
    else{
        if(!l) add++;
        if(!s) add++;
        if(!u) add++;
        if(!d) add++;
        
        if( (n+add)>=6 ) return add;
        else return add+abs(6-(n+add));
        
    }
}

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