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 ////////////////////
numbers = '0123456789';
lower_case = 'abcdefghijklmnopqrstuvwxyz';
upper_case = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
special_characters = '!@#$%^&*()-+';

function minimumNumber(n, password) {
  let i = 0;
  let j = {
    numbers: 0,
    lower_case: 0,
    upper_case: 0,
    special_characters: 0
  };
  while (i < n) {
    if (numbers.indexOf(password[i]) !== -1) j.numbers = 1;
    else if (lower_case.indexOf(password[i]) !== -1) j.lower_case = 1;
    else if (upper_case.indexOf(password[i]) !== -1) j.upper_case = 1;
    else if (special_characters.indexOf(password[i]) !== -1)
      j.special_characters = 1;
    i++;
  } // Return the minimum number of characters to make the password strong
  let r = 0;
  r += j.numbers;
  r += j.lower_case;
  r += j.upper_case;
  r += j.special_characters;

  let k = 0;
  if (r < 4) k = 4 - r;
  let ar = 0;
  if (n < 6) {
    ar = 6 - n;
  }
  if (ar > k) return ar;
  else {
    return k;
  }
}

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