N = int(input())
a = [0] * 10
while N != 0:
    a[N % 10] += 1
    N = N // 10
keta = sum(a)
"""
now = 0
t = 1
for i in range(keta):
    while True:
        if a[now] != 0:
            N += now * t
            t *= 10
            a[now] -= 1
            break
        else:
            now += 1
print(N)
"""
S = ''
for i in reversed(range(10)):
    S += str(i) * a[i]
print(int(S))