#include<iostream> #include<cstring> using namespace std; int main(){ char a[25]; cin>>a; if(a[0]>=48&&a[0]<=57){ cout<<"no"; return 0; } int len=strlen(a); for(int i=0;i<len;i++){ if((a[i]>=48&&a[i]<=57)||(a[i]>=65&&a[i]<=90)||(a[i]>=97&&a[i]<=122)||(a[i]==95)){ continue; }else { cout<<"no"; return 0; } } cout<<"yes"; return 0; }