#include<iostream>
#include<string>
using namespace std;
int main()
{
    string s;
    getline(cin, s);
    if(s.empty() || s.length() > 100 || s[0] == '-' || s.find('.') !=string::npos)
    {
        cout<<"INVALID INPUT";
        return 0;
    }
    for(char c : s)
    if(!isalnum(c))
    {
        cout<<"INVALID INPUT";
        return 0;
    }
    string rev = s;
    reverse(rev.begin(), rev.end());
    if (s == rev)
        cout<<"YES";
    else
        cout<<"NO";
    return 0;
}