#include<iostream>
#include<string>
using namespace std;
bool check (string s)
{
    for(char i:s)
    {
        if(!isalnum(i) && !(i ==' ' || i ==','))
        return true;
    }
    return false;
}
string lower()

int main()
{
    string s;
    getline(cin, s);
    if(s.size()>100)
    return 0;
    if(check(s))
    {
        cout<<"Invalid input";
        return 0;
    }
    string rs;
    for(int i=s.size()-1;i>=0;i--)
    {
        rs += tolower(s.at(i));
    }
    if(rs == s)
    {
        cout<<"YES";
    }
    else
    {
        cout<<"NO";
    }
    return 0;
}