#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define N 100005
using namespace std;
inline int read()
{
	int x=0,f=1;char ch=getchar();
	while(ch<'0' || ch>'9'){if(ch=='-') f=-1;ch=getchar();}
	while(ch>='0' && ch<='9'){x=(x<<3)+(x<<1)+(ch^48);ch=getchar();}
	return x*f;
}
int n,a[N];
inline double js(double p)
{
	double sum=0;
	for(int i=1;i<=n;i++)
	    if(a[i]<=int(2.0*p)) sum+=p;
	    else sum+=double(a[i])-p;
	return sum;
}
int main()
{
	n=read();
	for(int i=1;i<=n;i++) a[i]=read();
	sort(a+1,a+n+1);
	int l=1,r=n,lm,rm;
	while(l+1<r)
	{
		lm=(l+r)>>1;rm=(lm+r)>>1;
//		printf("%d %d %d %d\n",l,lm,rm,r);
		if(js(double(a[lm])/2.0)>js(double(a[rm])/2.0)) l=lm;
		else r=rm;
	}
	double ans=double(a[r])/2.0,P=0;
	for(int i=1;i<=n;i++)
	    if(a[i]<=int(2.0*ans)) P+=ans;
	    else P+=double(a[i])-ans;
	printf("%.6lf\n",P/double(n));
	return 0;
}
#include <stdio.h>
#include <cstring>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <iostream>
#include <map>

#define go(i, l, r) for(int i = (l), i##end = (int)(r); i <= i##end; ++i)
#define god(i, r, l) for(int i = (r), i##end = (int)(l); i >= i##end; --i)
#define ios ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0)
#define debug_in  freopen("in.txt","r",stdin)
#define debug_out freopen("out.txt","w",stdout);
#define pb push_back
#define all(x) x.begin(),x.end()
#define fs first
#define sc second
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> pii;
const ll maxn = 2e3+10;
const ll maxM = 1e6+10;
const ll inf_int = 1e8;
const ll inf_ll = 1e17;

template<class T>void read(T &x){
    T s=0,w=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
    while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
    x = s*w;
}
template<class H, class... T> void read(H& h, T&... t) {
    read(h);
    read(t...);
}

void pt(){ cout<<'\n';}
template<class H, class ... T> void pt(H h,T... t){ cout<<" "<<h; pt(t...);}

//--------------------------------------------
int a,b,c;
double dp[105][105][105];
double dfs(int a,int b,int c){
    if(a>=100 || b >= 100 || c >= 100) return 0;
    if(dp[a][b][c] >= -0.5) return dp[a][b][c];
    double ans = 0;
    ans += (double)a/(a+b+c) * dfs(a+1,b,c);
    ans += (double)b/(a+b+c) * dfs(a,b+1,c);
    ans += (double)c/(a+b+c) * dfs(a,b,c+1);
    return dp[a][b][c] = ans + 1;
}
int main() {
//    debug_in;
//    debug_out;

    read(a,b,c);
    go(i,0,101) go(j,0,101) go(k,0,101) dp[i][j][k] = -1;
    double ans = dfs(a,b,c);
    printf("%.8f\n",ans);
    return 0;
}