#include<cstdio>
#include<queue>
using namespace std;
 
int main()
{
	int great,least,n,i,x;
	long long sum;
	while(scanf("%d%d%d",&great,&least,&n), great&&least&&n)
	{
		priority_queue<int> q1;//从大到小出队
		priority_queue<int,vector<int>,greater<int> > q2;
		sum=0;
		for(i=0;i<n;i++)
		{
			scanf("%d",&x);
			sum+=x;
			q2.push(x);
			q1.push(x);
			if(q1.size()>least)
		   		q1.pop();
			if(q2.size()>great)
				q2.pop();
		}
		while(!q1.empty())
		{
			sum-=q1.top();
			q1.pop();
		}
		while(!q2.empty())
		{
			sum-=q2.top();
			q2.pop();
		}
		printf("%.6lf\n",1.0*sum/(n-great-least));
	}
	return 0;
}