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

int main(void){
    char str[30];
    int length = 0;
    
    scanf("%s",str);
    length = strlen(str);
    if ( 0 != (length % 2) ){
        length = (length / 2) + 1;
    }
    else{
        length = length / 2;
    }
    
    if ( 0 == strncmp(str+length,str, length) ){
        printf("YES\n");
    }
    else{
        printf("NO\n");
    }
    
    return 0; 
}