#include<iostream>
#include<string.h>
using namespace std;

int main()
{
	char ch[3000];
	int len,i,j;
	while(cin>>ch)
	{
		len = strlen(ch);
		if(len<3||len%2==0||ch[len/2]!='&')
		{
			cout<<"NO"<<endl;
			continue;
		}

		for(i = 0,j = len-1;i<j&&ch[i]>='a'&&ch[i]<='z'&&ch[i]==ch[j];i++,j--);

		if(i<j)
		{
			cout<<"NO"<<endl;
		}
		else
		{
			cout<<"YES"<<endl;
		}
	}
	return 0;
}
/**************************************************************
	Problem: 2225
	User: admin
	Language: C++
	Result: Accepted
	Time:47 ms
	Memory:2072 kb
****************************************************************/