#include<bits/stdc++.h> using namespace std; int main(){ string a; cin>>a; int n=a.size(); if(a[0]>='0'&&a[0]<='9'){ cout<<"no"; return 0; } for(int i=0;i<n;i++){ if(a[i]>='a'&&a[i]<='z')1+1==2; else if(a[i]>='A'&&a[i]<='Z')1+1==2; else if(a[i]>='0'&&a[i]<='9')1+1==2; else if(a[i]=='_')1+1==2; else{ cout<<"no"; return 0; } } cout<<"yes"; return 0; }