#include <bits/stdc++.h> using namespace std; int main(){ string n; cin>>n; if(n[0]>='0'&&n[0]<='9'){ cout<<"no"; return 0; } for(int i=0;i<n.length();i++){ if((n[i]>='0'&&n[i]<='9')||(n[i]>='A'&&n[i]<='Z')||(n[i]>='a'&&n[i]<='z')||n[i]==''){ continue; }else{ cout<<"no"; return 0; } } cout<<"yes"; return 0; } //@@dingsheng 感谢你的代码！！~~