process.stdin.resume();
process.stdin.setEncoding('ascii');

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////
const charClass = {
 numbers: "0123456789",
 lower_case: "abcdefghijklmnopqrstuvwxyz",
 upper_case: "ABCDEFGHIJKLMNOPQRSTUVWXYZ",
 special_characters: "!@#$%^&*()-+"
};

const getType = (letter) => Object.keys(charClass).find(cls => charClass[cls].includes(letter));

function minimumNumber(n, password) {
    password = password.substr(0,n)
    let requirements = {};
    for(const letter of password) {
        requirements[getType(letter)] = true;
    }
    const needRequirement = 4 - Object.keys(requirements).length;
    const needLength = 6 - password.length;
    const result = Math.max(needRequirement, needLength);
    return result > 0 ? result : 0;
}

function main() {
    var n = parseInt(readLine());
    var password = readLine();
    var answer = minimumNumber(n, password);
    process.stdout.write("" + answer + "\n");

}