import sys

def minimumNumber(n, password):
    l=[0,0,0,0]
    for c in password:
        if c in "0123456789":
            l[0] = 1
        elif c in "abcdefghijklmnopqrstuvwxyz":
            l[1] = 1
        elif c in "ABCDEFGHIJKLMNOPQRSTUVWXYZ":
            l[2] = 1
        elif c in "!@#$%^&*()-+":
            l[3] = 1
    if len(password) < 6:
        if l.count(0) == 0:
            return 6-len(password)
        else:
            return l.count(0) if l.count(0) > (6-len(password)) else 6-len(password)
    else:
        return l.count(0)

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