hdoj：2024

#include <iostream>
#include <string>
#include <vector>

using namespace std;
int main()
{
    int n;
    cin >> n;
    string s;
    bool flag = false;
    while (n >= 0)
    {
        flag = true;
        getline(cin, s);
        if (s.empty())
        {
            flag = false;
        }
        else
        {
            if (!(s[0] == '_' || isalpha(s[0])))
            {
                flag = false;
            }
            else
            {
                for (auto &c : s)
                {
                    if (c != '_' && !isalnum(c))
                    {
                        flag = false;
                        break;
                    }

                }
                
            }
            if (flag)
            {
                cout << "yes" << endl;
            }
            else
            {
                cout << "no" << endl;
            }
        }
        n--;
    }
    return 0;
}