C++ :

#include<bits/stdc++.h>
using namespace std;
int m;
int main()
{
//	freopen("1010.in","r",stdin);
//	freopen("1010.out","w",stdout);	
	cin>>m;
	if(m>=90 && m<=100) cout<<"A";
	else if(m>=80 && m<90) cout<<"B";
		  else if(m>=70 && m<80) cout<<"C";
		  		else if(m>=60 && m<70) cout<<"D";
				  	  else cout<<"E";	
	return 0;
}