#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>

using namespace std;

string s;
int n,r;
int main(){
	getline(cin, s);
	n = s.length();
	if(s[0] >= '0' && s[0] <= '9') cout << "no" << endl;
	else{
		for(int i = 0; i < n; i++){
			if((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z') || (s[i] >= '0' && s[i] <= '9') || s[i] == '_'){
				r++;
			} else {
				cout << "yes" << endl;
			}
		}
	}		
	if(r == n) cout << "yes" << endl;
	return 0;
}