#!/bin/python

import sys
numbers = "0123456789"
lower = "abcdefghijklmnopqrstuvwxyz"
upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
special = "!@#$%^&*()-+"


def minimumNumber(n, password):
    n, l, u, s = [False for _ in range(4)]
    for char in password:
        if char in numbers:
            n = True
        elif char in lower:
            l = True
        elif char in upper:
            u = True
        elif char in special:
            s = True
    
    needed = 4 - sum([n, l, u, s])
    return needed if len(password) + needed > 6 else 6 - len(password)
            

if __name__ == "__main__":
    n = int(raw_input().strip())
    password = raw_input().strip()
    answer = minimumNumber(n, password)
    print answer