难以言喻的一题，再一次感觉到了我的愚蠢

#include<iostream>
using namespace std;
#define MAX 100007
#define INF 0x3f3f3f3f

double l=1e5+7,r=0;
int n,f;
int a[MAX],s[MAX];

bool check(double ave){
	double sum1=s[f-1]-ave*(f-1);
	for(int i=f;i<=n;i++){
		double sum2=s[i]-s[i-f]-ave*f;
		sum1=sum1+a[i]-ave;
		sum1=max(sum1,sum2);
		if(sum1>-1e-5)return false;
	}
	return true;
}

double search(double L,double R){
	double mid;
	while(R-L>=1e-5){
		mid=(L+R)/2;
		if(check(mid))R=mid;
		else L=mid;
	}
	return R;
}

int main(){
	ios::sync_with_stdio(false);
	cin>>n>>f;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(a[i]>r)r=a[i];
		if(a[i]<l)l=a[i];
		s[i]=s[i-1]+a[i]; 
	}
	
	double ans=search(l,r);
	cout<<(int)(ans*1000);
	return 0;
}