#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 +=tolower(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;
     
 }