Recently, Anton has found a set. The set consists of small English letters. Anton carefully wrote out all the letters from the set in one line, separated by a comma. He also added an opening curved bracket at the beginning of the line and a closing curved bracket at the end of the line. 

Unfortunately, from time to time Anton would forget writing some letter and write it again. He asks you to count the total number of distinct letters in his set.
The first and the single line contains the set of letters. The length of the line doesn't exceed 1000. It is guaranteed that the line starts from an opening curved bracket and ends with a closing curved bracket. Between them, small English letters are listed, separated by a comma. Each comma is followed by a space.
n = 1000  # 最大长度
strs = ""  # 输入字符串
len = 0  # 字符串长度


# 输入函数
def input_str():
    global strs, len
    print("请输入一行长度在{}以内、仅包括小写字母、‘{’、‘}’ 和空格的字符串：".format(n))
    strs = input()  # 从标准输入读取一行字符串
    len = len(strs)
    if len > n:
        print("输入字符串长度超过 {}！".format(n))
    for i in range(len):
        c = strs[i]
        if not(c >= 'a' and c <= 'z' or c == '{' or c == '}' or c == ' '):
            print("输入不合法")
            break


# 统计函数
def stat_str():
    global strs, len
    char_set = set()  # 统计字符种类
    for c in strs:
        if c >= 'a' and c <= 'z':
            char_set.add(c)
    return len(char_set)


if __name__ == '__main__':
    input_str()  # 输入字符串
    j = stat_str()
    print(j)

	 	   			 			            						