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

#ifndef INPUT_FROM_STDIN
#define INPUT_FROM_STDIN 1
#endif

int twotimes(const char * s, size_t len) {	/* s MAY contain a null character ('\0') */
    size_t m = len / 2;
    if (len - m != m)
	return 0;
    for (size_t i = 0; i < m; ++i)
	if (s[i] != s[i + m])
	    return 0;
    return 1;
}

#if INPUT_FROM_STDIN
int main(int argc, const char * argv[]) {
    char buf[1000];
    if (fgets(buf, 1000, stdin)) {
	size_t len = strlen(buf);
	if (buf[len - 1] == '\n')
	    len = len - 1;
	printf("%s\n", twotimes(buf, len) ? "YES" : "NO");
    } else {
	printf("Error\n");
    }
}
#else
int main(int argc, const char * argv[]) {
    int i;
    /* iterate through the command-line arguments */
    for (i = 1; i < argc; ++i) 
	printf("'%s' %s\n", argv[i], twotimes(argv[i], strlen(argv[i])) ? "YES" : "NO");
}
#endif