temp = input()
data = []
ace = []
for i in temp:
    if i in data:
        ace[data.index(i)] += 1
    else:
        data.append(i)
        ace.append(1)
p = min(ace)
for i in temp:
    if ace[data.index(i)] != p:
        print(i,end="")
    else:
        continue

输入：aabcddd

输出：aaddd