#include <bits/stdc++.h> using namespace std; int main() { char s[25]; cin>>s; int q=0; for(int i=0;i<strlen(s);i++){ if(s[0]>='0' && s[0]<='9'){ q=1; } if(s[i]<'0' || (s[i]>'9' && s[i]<'A') || (s[i]>'Z' && s[i]<'_') || (s[i]>'_' && s[i]<'a')|| s[i]>'z' ){ q=1; } } if(q==1){ cout<<"no"<<'\n'; } else{ cout<<"yes"<<'\n'; } return 0; }