#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,n,sum=0,cnt=0;
	cin>>a>>b>>n;
	for(int i=1;i<=n;i++){
		int x;
		cin>>x;
		if(x<a||x>b) cnt++;
		else sum+=x;
	}
	if(cnt>n*0.1) cout<<"0.0";
	else printf("%.1f",(double)sum*1.0/(n-cnt));
	return 0;
}