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

int main()
{
	char* S, * front, * back;
	int len;

	S = (char*)malloc(sizeof(char) * 20);

	if (scanf("%s%n", S, &len) != 1) {
		return -1;
	}

	if (len%2 != 0) {
		printf("NO");
		return 0;
	}

	front = (char*)malloc(sizeof(char) * (len / 2) + 1);
	back = (char*)malloc(sizeof(char) * (len / 2) + 1);

	if (S == NULL || front == NULL || back == NULL) {
		return -1;
	}

	front[len / 2] = '\0';
	back[len / 2] = '\0';

	for (int i = 0; i < len; i++) {
		if (i < (len / 2)) {
			*(front + i) = *(S + i);
		}
		else {
			*(back + i - (len / 2)) = *(S + i);
		}
	}
	if (strcmp(front, back) != 0) {
		printf("NO");
		return 0;
	}

	printf("YES");

	free(S);
	free(front);
	free(back);

	S = NULL;
	front = NULL;
	back = NULL;

	return 0;
}