#include<bits/stdc++.h>
#include <iomanip>
#include <ios>
#define ll long long
#define N 9999
#define sp << " "<<
#define mp make_pair
using namespace std;

ll n,m,b,sum,t,a,c;
ll ans1,ans2,ans3,cnt;
int s[N];
int main()
{
    
    cin>>a>>b>>c;
    for(int i=1;i<=c;i++)
    {
        cin>>t;
        if(t>=a&&t<=b) sum+=t;
        else cnt++;
    }
    if(cnt*10>c) cout<<"0.0";
    else cout<<fixed<<setprecision(1)<<(double)(static_cast<double>(sum)/(c-cnt));
    return 0;   
}