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

int main(void){
    int len,i=0;
    char in[21],rslt[4],half[21],tmp[21];

    fgets(in,sizeof(in),stdin);
    for(i=0;in[i]!='\n';i++){
        if(i==20)break;
    }
    strncpy(half,in,i/2);
    strcpy(tmp,half);
    strcat(tmp,half);
    len=strncmp(tmp,in,i);

    if(len==0){
        strcpy(rslt,"YES");
    }else{
        strcpy(rslt,"NO");
    }

    printf("%s\n",rslt);
    return 0;
}