#include <iostream>
#include <math.h>
using namespace std;
int main()
{
int f;
while(cin>>f){
if(f>=90 && f<=100)
{cout<<"A"<<endl;}
else if(f>=80 && f<90)
{cout<<"B"<<endl;}
else if(f>=70 && f<80)
{cout<<"C"<<endl;}
else if(f>=60 && f<70)
{cout<<"D"<<endl;}
else if(f>=0 && f<60)
{cout<<"E"<<endl;}
else
{cout<<"Score is error!"<<endl;}
}
return 0;
}