import Foundation
let n = Int(readLine()!)!
let string = readLine()!

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

var counter = 0
for ch in string.characters {
    if numbers.contains(ch) {
        counter += 1
        numbers = ""
    }
    if lower_case.contains(ch) {
        counter += 1
        lower_case = ""
    }
    if upper_case.contains(ch) {
        counter += 1
        upper_case = ""
    }
    if special_characters.contains(ch) {
        counter += 1
        special_characters = ""
    }
}

if string.characters.count >= 6 {
    print(4 - counter)
} else {
    if (6 - string.characters.count) > (4 - counter) {
        print(6 - string.characters.count)
    } else {
        print(4 - counter)
    }
}