python 刪除字符串中出現次數最少的字符

import sys
for in_str in sys.stdin:
    cha=[]
    num=[]
    for elem in in_str:
        if elem not in cha:
            cha.append(elem)
            num.append(1)
        else:
            num[cha.index(elem)]+=1
    # 找到num列表中最小的元素數值在num中的索引值（可能不止一個最小元素值）

    min_v=min(num)
    delete_cha=[]
    for i,elem in enumerate(num):
        if elem==min_v:
            delete_cha.append(cha[i])
    # print(delete_cha)
    # output_str=in_str.copy()
    for elem in in_str:
        if elem in delete_cha:
            in_str=in_str.replace(elem,'')
    print(in_str)