#include<iostream> using namespace std; int main(){ char a; cin>>a; if(a>=90){ cout<<'A'<<endl; } else if(80<=a<90){ cout<<'B'<<endl; } else if(70<=a<80){ cout<<'C'<<endl; } else if(60<=a<70){ cout<<'D'<<endl; } else{ cout<<"不及格"<<endl; } return 0; }