#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=50000+5;
const double eps=1e-3;
int n;
ll x[N],b[N];
ll lmn[N],rmn[N]; 
bool check(double mid){
	for (int i=n;i>=1;i--){
		if (1.0*lmn[i]<=mid-1){
			int l=upper_bound(x+i+1,x+n+1,1.0*x[i]+2.0*mid)-x-1;
			if (1.0*rmn[l]<=mid-1)return 1;
			else return 0;
		}	
	}
	return 0;
}
int main(){
	freopen ("angry.in","r",stdin);
	freopen ("angry.out","w",stdout);
	scanf("%d",&n);
	for (int i=1;i<=n;i++)scanf("%lld",&x[i]);
	sort(x+1,x+n+1);
	memset(lmn,0x3f,sizeof(lmn));
	lmn[1]=0;b[1]=lmn[1]+1+x[1];
	for (int i=2;i<=n;i++){
		int l=lower_bound(b+1,b+i,x[i])-b;
		lmn[i]=min(max(lmn[l-1]+1,x[i]-x[l-1]),max(lmn[l]+1,x[i]-x[l]));
		b[i]=lmn[i]+1+x[i];
	}
	memset(rmn,0x3f,sizeof(rmn));
	rmn[n]=0;b[n]=x[n]-rmn[n]-1;
	for (int i=n-1;i>=1;i--){
		int l=lower_bound(b+i+1,b+n+1,x[i])-b;
		rmn[i]=min(max(rmn[l-1]+1,x[l-1]-x[i]),max(rmn[l]+1,x[l]-x[i]));
		b[i]=x[i]-rmn[i]-1;
	}
	double l=1,r=x[n]-x[1];
	while(fabs(l-r)>eps){
		double mid=(l+r)/2;
		if (check(mid))r=mid;
		else l=mid;
	}
	printf("%.1lf\n",l);
	return 0;
}