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

int main(){
    string s,getline(cin,s);
    if(s.empty() || s.find(',') != string::npos ||
    (s[0]=='-' && s.size()>1 && all_of(s.begin()=1,s.end();::isdigit))||
    !all_of(s.begin(),s.end(), ::isalnum))
    cout<< "INVALID INPUT";
else {
    string r=s;reverse(r.begin(),r.end());
    cout << (s==r ? "YES" : "NO");
    }
     return 0;
}