使用ascil码做标记，对比ascil码即可

str1 = str(input())

asc = []
k = 0

for i in str1:
    flag = 0
    for j in asc:
        if ord(i) == j:
            flag = 1

    if flag == 0:
        asc.append(ord(i))
        k += 1

print(k)