题解

#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    double n,a=0,b=0;
    cin>>n;
    a=n*0.5;
    if(n<=100){
        b=n*0.3;
    }else{
        b=100*0.3+(n-100)*0.6;
    }
    if(a>b){
        cout<<'B'<<endl;
        printf("%.1f",b);
    }else{
        cout<<'A'<<endl;
        printf("%.1f",a);
    }
    return 0;
}