#include<iostream> #include<cstring> using namespace std; int main() { char s[20],cnt=0; cin>>s; for(int i=0;i<strlen(s);i++){ if(s[i]>='A'&&s[i]<='Z'||s[i]>='a'&&s[i]<='z'||s[i]=='_'||s[i]>='0'&&s[i]<='9'){ cnt++; } } if(strlen(s)==cnt&&s[0]<'0'||strlen(s)==cnt&&s[0]>'9'){ cout<<"yes"; } else{ cout<<"no"; } }