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