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