include <bits/stdc++.h>

using namespace std;

double a, b, c;

int main() {
cin >> a >> b >> c;
double t = (a + b + c) / 3;
if (t >= 8.0)
cout << "gioi";
else if (t >= 6.5)
cout << "kha banh";
else if (t >= 5.0)
cout << "trung binh";
else
cout << "yeu";

return 0;

}