#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() using namespace std; int main(){ int n; cin>>n; n=n/10; switch(n){ case 10: case 9: cout<<'A';break; case 8: case 7: cout<<'B';break; case 6:cout<<'C';break; default:cout<<'D';break; } return 0; }