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

int main()
{
    string s;
    while(cin>>s){
        bool isOk=true;
        stack<string> stk;

        for( int i=s.length()-1 ; i>=0 ; i--){
            string sentence;

            if(s[i]>='p' && s[i]<='z'){
                sentence = s[i];
                stk.push(sentence);
            }
            else if(s[i] == 'N'){
                if( stk.empty() ){
                    isOk = false;
                    break;
                }
                sentence = 'N' + stk.top();
                stk.pop();
                stk.push(sentence);
            }
            else if( s[i] == 'C' || s[i] == 'D' || s[i] == 'E' || s[i] == 'I' ){
                if(stk.size()<2 ){
                    isOk = false;
                    break;
                }
                sentence = stk.top();
                stk.pop();
                //sentence = s[i]+ sentence + stk.top();
                sentence = s[i]+ stk.top() + sentence;
                stk.pop();
                stk.push(sentence);
            }
            else{
                isOk = false;
                break;
            }
        }
        if(stk.size()!=1){
            isOk = false;
        }
        cout<<((isOk)? "YES":"NO")<<endl;
    }
    return 0;
}