// yuki 1643 Not Substring
// 2021.8.13

#include <stdio.h>

char S[105];
int main()
{
	char *s;
	scanf("%s", s = S);
	int w = 0;
	while (*s) {
		if (*s == 'a') {
			char *p = s++; while (*s == 'a') s++;
			w += s-p;
		} else s++;
	}
	while (w--) putchar('a');
	puts("a");
	return 0;
}