#include<iostream>
using namespace std;
int main()
{
int x;
while(cin>>x)
{
if(100>=x&&x>=90)
cout<<"A"<<endl;
else if(89>=x&&x>=80)
cout<<"B"<<endl;
else if(79>=x&&x>=70)
cout<<"C"<<endl;
else if(69>=x&&x>=60)
cout<<"D"<<endl;
else if(59>=x&&x>=0)
cout<<"E"<<endl;
else
cout<<"Score is error!"<<endl;
}
}