#include
#include
int main(void)
{
char a[101],s[101];
int i,len,mid,next,top;
gets(a);
len=strlen(a);
mid=len/2-1;
top=0;
for (i = 0; i <=mid ; ++i) {
s[++top]=a[i];
}
if (len%2==0) {
next=mid+1;
} else {
next=mid+2;
}
for (i = next; i <=len-1; ++i) {
if (a[i]!=s[top]) {
break;
}
top--;
}
if (top==0) {
printf("YES\n");
} else {
printf("NO\n");
}
return 0;
}