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 numbers = "0123456789".split('')
const lowerCase = "abcdefghijklmnopqrstuvwxyz".split('')
const upperCase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split('')
const specialCharacters = "!@#$%^&*()-+".split('')

function minimumNumber(n, password) {
    // Return the minimum number of characters to make the password strong
    
    let hasNumber = false;
    let hasLowerCase = false;
    let hasUppercase = false;
    let hasSpecialCharacter = false;
    let total = 0;
    
    for (let i = 0 ; i < n ; ++i) {
        if (!hasNumber && numbers.includes(password[i])) {
            hasNumber = true;
            total++;
        }
        if (!hasLowerCase && lowerCase.includes(password[i])) {
            hasLowerCase = true;
            total++;
        }
        if (!hasUppercase && upperCase.includes(password[i])) {
            hasUppercase = true;
            total++;
        }
        if (!hasSpecialCharacter && specialCharacters.includes(password[i])) {
            hasSpecialCharacter = true;
            total++;
        }
        
        if (total === 4) {
            break;
        }
    }
    
    return Math.max(4 - total, 6 - n);
}

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

}