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

int main(){
    string s;
    getline(cin, s);
    
    if(s.length() > 100){
        cout <<"INVALID INPUT";
        return 0;
    }
    string clean = "";
    for(char c : s){
        if(isalnum(c))
           clean +=tolower(c);
        else if(c!='')
        {
            cout << "INVALID INPUT";
            return 0;
        }
    }
    if(clean.empty()){
        cout << "INVALID INPUT";
        return 0;
    }
    string rev = clean;
    reverse(rev.begin(), rev.end());
    
    if(clean == rev)
       cout << "YES";
    else
        cout << "NO";
    return 0;    
}