//解密回文--栈
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 55
int main()
{
    char a[N], s[N];
    int i, len, mid, next, top;
    while(gets(a))
    {
        len = strlen(a);//求字符串的长度;
        mid = len/2 - 1;//求字符串的中点;
        top = 0; //栈的初始化;
//将mid前的字符依次入栈;
        for(i = 0; i <= mid; i++)
        {
            s[++top] = a[i];
        }
//判断字符串的长度是奇数还是偶数,并找出需要进行字符匹配的起始下标;
        if(len % 2 == 0) next = mid + 1;
        else next = mid + 2;
//开始匹配;
        for(i = next; i <= len - 1; i++)
        {
            if(a[i] != s[top])
                break;
            top--;
        }
//如果top的值为0,则说明栈内所有的字符都被一一匹配了;
        if(top == 0)
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;

}