题解

#include<bits/stdc++.h>
using namespace std;
int main()
{
int a;
while(cin>>a)
{
if(a>100)
{
cout<<"输入错误，请重新输入！";
}
else if(a>=90)
{
cout<<"A";
}else if(a>=80)
{
cout<<"B";
}
else if(a>=60)
{
cout<<"C";
}else
{
cout<<"D";
}
}
return 0;
}