#include<bits/stdc++.h>
using namespace std;
int main() {
    string s,t="";
    getline(cin,s);
    if(s[0]=='-'||s.find('-')!=string::npos) {
        cout<<"INVALID INPUT";
        return 0;
    }
    for(char c :: s)
    if(isalnum(c)) t += tolower(c);
    string r=t;
    reverse(r.begin(), r.end());
    cout<< (t== r ?"YES" : "NO");
    return 0;
}