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