#include<iostream>
using namespace std;
int main()
{
    int a;
    cout<<"请输入一个整数:";
    cin>>a;
    cout<<a<<endl;
    if(a>=0&&a<=100)
    {
        switch(a/10)
            {
            case 10:
            case 9:
        cout<<"等级A"<<endl;
        break;
        case 8:
        cout<<"等级B"<<endl;
        break;
        case 7:
        cout<<"等级C"<<endl;
        break;
        case 6:
        cout<<"等级D"<<endl;
        break;
        default:
        cout<<"不及格"<<endl; 
        break;
            }
    }
        else
        cout<<"输入错误"<<endl;
      return 0;  
}