#include <stdio.h>
#include <string.h>

void bubbleSort(char* s) {
    int len = strlen(s);
    char temp;
    for (int i = 0; i < len; i++) {
        for (int j = 0; j < len - 1; j++) {
            if (s[j] > s[j + 1]) {
                temp = s[j];
                s[j] = s[j + 1];
                s[j + 1] = temp;
            }
        }
    }
}

int main() {
    char s[21];
    while (scanf("%s", &s) != EOF) {
        bubbleSort(s);
        printf("%s\n", s);
    }
    return 0;
}