n=list(map(int,input()))
ans=""
ans_2=""
for i in range(len(n)):
    ans_2+=str(n[i])
n.sort()
a=n[::-1]
for i in range(len(n)):
    ans+=str(a[i])
    
if ans_2<ans:
    print(ans)
else:
    print(ans_2)