#!/bin/python3

import sys

def minimumNumber(n, p):
    # Return the minimum number of characters to make the password strong
    num=1
    sp=1
    cap=1
    low=1
    if len(p)>=6:
        l=0
    else:
        l=6-len(p)
    for i in range(len(p)):
        if p[i].isdigit():
            num=0
        elif p[i].isupper():
            cap=0
        elif p[i].islower():
            low=0
        else:
            sp=0
        if num==sp==cap==low==0:
            break
    if l==0:
        return num+sp+cap+low
    elif l>=num+sp+cap+low:
        return l
    else:
        return num+sp+cap+low
if __name__ == "__main__":
    n = int(input().strip())
    password = input().strip()
    answer = minimumNumber(n, password)
    print(answer)