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

bool ispalindrome(string s)
{
    string rev = s;
    reverse(rev.begin(), rev.end());
    return s == rev;
}
bool isValidInput(string s)
{
    if(s.length() == 0 || s.length() > 100)
    return false;
    for(char c:s )
    {
        if(!isalnum(c))
        return false;
    }
    if(s.find('.') != string::npos || s.find('-') != string::npos)
    return false;
  return true;
}
 
int main()
{
    string input;
    getline(cin, input);
    if(!isValidInput(input))
    {
        cout<<"INVALID INPUT";
        return 0;
    }
    if (ispalindrome(input)
        cout<<"YES";
   
    return 0;
}