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

#define MAX 1000000

int main(void) {
	char n[MAX + 1];
	int bit, temp;

	scanf("%s", n);

	bit = strlen(n);

	for (int i = 0; i < bit - 1; i++)
		for (int j = i + 1; j < bit; j++)
			if (n[i] < n[j])
				temp = n[i], n[i] = n[j], n[j] = temp;

	printf("%s\n", n);

	return 0;
}