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

int main() {
    string s,t="";
    getline(cin,s);
    if(s.find('-')!=string::npos||s.find('-')!=string::npos){
        cout<<"INVALID INPUT";
        return 0;
    }
    for(char c:s)
        if(!isalnum(c)+=tolower(c){
    if(t.empty()){
        cout<<"INVALID INPUT";
        return 0;
    }
    string r=t;reverse(r.begin(),r.end());
    cout<<(t==r?"YES":"NO");
}