#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main(){
    string input;
    getline(cin, input);
    
    if (input.length() > 100) {
        cout << "INVALID INPUT";
        return 0;
    }
    if (input[0] == '_'){
        cout<< "INVALID INPUT";
        return 0;
    }
} 
    string clean ="";
 
     for (char c : input) {
     if (c == '.')
{
    cout << "INVALID INPUT";
    RETURN 0;
}
         
     }
      string clean ="";
      for (char c : input){
          if (isalnum(c)) {
              clean +=tolowerr(c):
          }
      }
      int i =0,j=clean.length() -1;
      while (i<j) {
          if (clean[i] !=clean[j]){
              cout <<"NO";
              return 0;
          }
          i++;
          j--;
      }
      cout << "YES";
      return 0;
     
 }