# include<iostream> using namespace std; int main(){ string a; int b; 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]=='_'){ b=1; } else b=0; } if(b==0)cout<<"no"; if(b==1)cout<<"yes"; return 0; }