20pts求助

#include<iostream>
#include<cstdio>
using namespace std;
int n;
double A,B;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        double a;
        cin>>a;
        A+=a;
    }
    for(int i=1;i<=n;i++){
        double b;
        cin>>b;
        B+=b;
    }
    printf("%.6lf",(A*3.0-B*2.0)/(A-B));
    cout<<endl;
    return 0;
}