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

int main() {
    string s;
    getline (cin, s);
    
    if(s.length() == 0 || s.length() > 100) {
        cout << "INVALID INPUT";
        return 0;
    }
    
    string cleaned = "";
    
    for (char c : s) {
        if (isalnum(c)) {
            cleaned +=tolower(c);
            hasAlphaNum = true;
        } else if (c == ' ' || c == ',' || c == '.') {
            continue;
        } else {
            cout<< "INVALID INPUT";
            return 0;
        }
    }
    if (!hasAlphaNum) {
        cout << "INVALID INPUT";
        return 0;
    }
    int i= 0, j = cleaned.length() - 1;
    while (i < j) {
        if (cleaned[i] != cleaned[j]) {
            cout << "NO" ;
            return 0;
        }
        i++;
        j--;
    }
    
    cout << "YES" ;
    
    return 0;
}