n = int(input())
s = input()
num = 0
low = 0
up = 0
special = 0
for i in s:
if '0' <= i <= '9':
num = 1
elif 'a' <= i <= 'z':
low = 1
elif 'A' <= i <= 'Z':
up = 1
else:
special = 1
must = 4 - (num + low + up + special)
print(max(must, 6-len(s)))