题解

#include<bits/stdc++.h>
using namespace std;
int main(){
double a;
cin>>a;
if(a<10.0)cout<<'A';
else if(a>=10.0 and a<20.0)cout<<"B";
else if(a>=20.0 and a<40.0)cout<<'C';
else if(a>=40.0 and a<50.0)cout<<"D";
else cout<<'E';
}