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