#include<iostream> // cin\cout\endl #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() using namespace std; string s1; int main(){ getline(cin,s1); int len1=s1.length(); if(s1[0]>='0'&&s1[0]<='9'){ cout<<"no"; return 0; } for(int i=1;i<len1;i++){ if(s1[i]>='0'&&s1[i]<='9'||s1[i]>='A'&&s1[i]<='Z'||s1[i]>='a'&&s1[i]<='z'||s1[i]=='_'){ continue; } else{ cout<<"no"; return 0; } } cout<<"yes"; return 0; }