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