#include <iostream>
using namespace std;
int main(){
	string a;
	cin>>a;
	bool d=true;
	if(a=="int"||a!="cin"||a=="cout"||a=="double"||(a[1]<='9'&&a[1]>='1')){
		d=false;
	}
	for(int i=0;i<a.size();i++){
		if(a[i]!='_'||!(a[i]<='9'&&a[i]>='1')||!(a[i]<='Z'&&a[i]>='A')||!(a[i]<='z'&&a[i]>='a')){
			d=false;
		}
	}
	if(d==true){
		cout<<"yes";
	}else{
		cout<<"no";
	}
    return 0;
}
/**************************************************************
	Problem: 1408
	User: panyuchen
	Language: C++
	Result: Wrong Answer
****************************************************************/