#include <iostream>
using namespace std;
int main() {
    int a = 11, b = 20;
    if (a > b) {
        cout << "A";
    } else if (a + 5 > b) {
        cout << "B";
    } else if (a * 2 > b) {
        cout << "C";
    } else {
        cout << "D";
    }
    return 0;
}