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