#include<stdio.h>
#include<stdlib.h>
int cmp ( const void *a , const void *b )
{
return *(long *)a - *(long *)b;
}
void main()
{
	long max,min,n,i,j;__int64 sum;
	long a[50001];
	while(scanf("%ld%ld%ld",&max,&min,&n))
	{
		sum=0L;
		if(max==0&&min==0&&n==0)break;
		else 
		{
			for(i=0;i<n;i++)
				scanf("%ld",&a[i]);
			//quicksort(a,0,n-1);
			qsort(a,n,sizeof(a[0]),cmp); 
			for(j=min;j<n-max;j++)
				sum+=a[j];
			printf("%.6lf\n",(double)(sum)/(double)(n-min-max));
		}
	}
}