#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
using namespace std;
int main()
{
    string s;
    getline(cin,s);
   if(s[0]=='-'||s.find('.')!=string::npos)
   {
       cout<<"INVALID INPUT";
       return 0;
   }
   string t="";
   for(char c:s)
   {
       if(isalnum(c))
       t==tolower(c);
   }
   if(t=="")
   {
       cout<<"INVALID INPUT";
       return 0;
   }
   string r=t;
   reverse(r.begin(), r.end());
   if(t==r)
   cout<<"YES";
   else 
   cout<<"NO";
}