#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
using namespace std;
bool ispallindrome(string s){
    string cleaned ='';
    for(char c:s){
        if(isalnum(c)){
            
        }
    }
    string reversed = cleaned;
    reversed(reversed.begin(),reversed.end());
    return cleaned == reversed;
    
}
bool isvalidinput(string s){
    if(s.length(>1100||s.empty())
    return false;
    
    if s[0=='-']
    return false;
    for char(c:s){
        if(!(isalnum(C)||isspace(c)|| c==',')){
    }
    if(c=='-')
    return false;
}
    return true;
    {
     int main(){
         string input;
         getline(cin,input);
         if(!isvalidinput(input)){
             cout<<"INVALID INPUT";
         }
     }
     else{
         if(ispallindrome(input))
         cout<<"YES";
         else
         cout<<"NO";
     }
     
 }
 return 0;
}