A450.等级测评，题解

#include<bits/stdc++.h>
using namespace std;
int main()
{
int n;cin>>n;
if(n>=90 and n<=100){
cout<<"A"<<endl;
}else if(n>=80 and n<=89){
cout<<"B"<<endl;
}else if(n>=70 and n<=79){
cout<<"C"<<endl;
}else if(n>=60 and n<=69){
cout<<"D"<<endl;
}else cout<<"E"<<endl;
return 0;
}