#include<bits/stdc++.h>
#define int long long
#define INF 0x3f3f3f3f
#define INFSHORT 1e+3
#define INFINT 1e+10
#define INFLONGLONG 1e+19
using namespace std;
string a;
signed main(){
	cin>>a;
	for(int i=0;i<a.size();i++){
	    if(i==0) if(a[i]>=48&&a[i]<=57){
				 	 puts("no");
					 return 0;
				 }
	    if (a[i]>='a'&&a[i]<='z') continue;
		else if(a[i]>=48&&a[i]<=57) continue;
		else if(a[i]=='_') continue;
		else {
			puts("no");
			return 0;
		}
	}
	puts("yes");
}

只有90分，别抄（what）