#include <iostream>
#define MAXSIZE 100
#define OK 1
#define ERROR 0
#define OVERFLOW - 2
using namespace std;
typedef struct {
char * base;
char * top;
int stacksize;
}
SqStack;
int InitStack(SqStack & S) { //栈初始化
S.base = new char[MAXSIZE];
if (!S.base) return OVERFLOW;
S.top = S.base;
S.stacksize = MAXSIZE;
return OK;
}
int Push(SqStack & S, char e) { //入栈
if (S.top - S.base == S.stacksize) //栈满
return ERROR;
* S.top = e;
S.top++;
return OK;
}
int Pop(SqStack & S) { //出栈返回栈顶元素
if (S.top == S.base) //栈空
return ERROR;
S.top--;
return * S.top;
}
int IsPalindrome(SqStack & S, char * t) { //判断栈的回文字符序列
/**************begin************/
/**************end************/
}
int main() {
char t[100];
while (cin >> t && t[0] != '0') {
SqStack S;
InitStack(S);
if (IsPalindrome(S, t) == 1) cout << "YES" << endl;
else cout << "NO" << endl;
}
return 0;
}
