#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min()\fabs() #include<ctime> #include<cstdlib> #include<cstring> using namespace std; int main(){ string a; getline(cin,a); if(a[0]<='9' && a[0]>='0'){ cout<<"no"; return 0; } for(int i=0;i<a.size();i++){ if(!((a[i]<='9' && a[i]>='0') || (a[i]<='z' && a[i]>='a') || (a[i]<='Z' && a[i]>='A') || a[i]=='_')){ cout<<"no"; return 0; } } cout<<"yes"; return 0; }