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 ////////////////////
function password(str) {
  const numbers = "0123456789";
  const lowerCase = "abcdefghijklmnopqrstuvwxyz";
  const upperCase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  const specialCharacters = "!@#$%^&*()-+";
  
  let needed = {
    num: false,
    lc: false,
    uc: false,
    sch: false,
  };
  
  for (let i = 0; i < str.length; i++) {
    if (~numbers.indexOf(str[i])) 
      needed.num = true;
    if (~lowerCase.indexOf(str[i]))
      needed.lc = true;
    if (~upperCase.indexOf(str[i]))
      needed.uc = true;
    if (~specialCharacters.indexOf(str[i]))
      needed.sch = true;
  }
  
  let numOfTrues = 0;

  for (let prop in needed)
    if (needed[prop] === true)
      numOfTrues++;
  
  if (str.length >= 6 && numOfTrues == 4)
    return 0;
  else if (str.length >= 6)
    return 4 - numOfTrues;
  else 
    return 6 - str.length > 4 - numOfTrues ? 6 - str.length : 4 - numOfTrues;
}

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

}