#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(void) {
	while (1) {
		if (rename("0/1/2/3/4/5/6/7/8/9", "0_"))
			perror("rename a");
		if (rename("0_", "0/1/2/3/4/5/6/7/8/9"))
			perror("rename b");
	}
}