#include <stdio.h>
#define L 40

void effe(char *s) {
	char tmp;
	int i, j;
	for(i = 0; s[i] != 0; i++)
		for(j = i + 1; s[j] != 0; j++)
			if(s[i] > s[j]) {
				tmp = s[i];
				s[i] = s[j];
				s[j] = tmp;
		}
}


main () {
	char array[L];
	effe(gets(array));
	printf("%s\n", array);
	return 0;
}