#include <iostream>
using namespace std;
int main() {
int t,n,d[10]={0,};
cin>>n;
while(1) {
++d[n%10];
n/=10;
if(n==0) break;
}
t=0;
for(int i=9;i>=0;--i) {
if(d[i]) {
while(d[i]--) {
t *= 10;
t+=i;
}
}
}
cout << t;
}
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