strin = input()
slist = list(strin)
min_list={}
for y in slist:
    min_list[y]=slist.count(y)
mins = min(min_list.values())
D=[]
for s in strin:
    if min_list[s]!= mins:
       D.append(s) 
    else:
        continue       
result = ''.join(D)
print(result)