#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
#define maxn 25
using namespace std;
char c[maxn];

bool cmp(char c1,char c2)
{
    return c1<c2;
}


int main() {
    scanf("%s",c);
    int len = strlen(c);
    sort(c,c+len,cmp);
    for(int i=0;i<len;i++)cout<<c[i];
    cout<<endl;
}
// 64 位输出请用 printf("%lld")