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