一本通1134

#include <bits/stdc++.h>
#define rep(i,j,n) for(register int i=j;i<=n;i++)
#define Rep(i,j,n) for(register int i=j;i>=n;i--)
#define low(x) x&(-x)
using namespace std ;
typedef long long LL ;
const int inf = INT_MAX >> 1 ;
inline LL In() { LL res(0) , f(1) ; register char c ;
#define gc c = getchar()
    while(isspace(gc)) ; c == '-' ? f = - 1 , gc : 0 ;
    while(res = (res << 1) + (res << 3) + (c & 15) , isdigit(gc)) ;
    return res * f ;
#undef gc
}

string s ;
inline void Ot() {
	getline(cin , s) ;//cin >> s ;
	int len = s.length() ;
	if(isdigit(s[0])) {
		puts("no") ;
		return ;
	}
	for(register int i=0;i<len;i++){
		if(!isalpha(s[i]) and !isdigit(s[i]) and s[i] != '_') {
			puts("no") ;
			return ;
		}
	}
	puts("yes") ;
}
signed main() {
//  freopen("test.in","r",stdin) ;
    return Ot() , 0 ;
}