#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <set>
#include <iomanip>
#include <map>
#include <cmath>
#include <queue>
#include <cstdlib>

using namespace std;

#define pb push_back
#define ll long long

int mode = 1000 * 1000 * 1000 + 7;
int main()
{
    ios_base::sync_with_stdio(false);

    int n;
    cin >> n;

    vector<double> v(n);

    for(int i = 0; i < n; ++i)
    {
        cin >> v[i];
    }

    sort(v.begin(), v.end());

    vector<double> len(n - 1);
    vector<double> poss;

    double mx = 0;
    for(int i = 0; i < n - 1; ++i)
    {
        len[i] = v[i + 1] - v[i];
        if(len[i] > mx)
        {
            poss.clear();
            mx = len[i];
            poss.pb(i);
        }
        else if(len[i] == mx)
        {
            poss.pb(i);
        }
    }

    cout << setprecision(1) << fixed;
    if(n == 2)
    {
        cout << len[0] / 2 << endl;
        return 0;
    }

    double ans = mx;
    for(int i = 0; i < poss.size(); ++i)
    {
        double ans2 = mx / 2, need = 1;
        for(int j = poss[i] - 1; j >= 0; --j)
        {
            if(ans2 - need < len[j])
            {
                ans2 += len[j] + need;
            }
            ++need;
        }

        need = 1;

        for(int j = poss[i] + 1; j < n - 1; ++j)
        {
            if(ans2 - need < len[j])
            {
                ans2 = need + len[j];
            }
            ++need;
        }

        ans = min(ans, ans2);
    }

    cout << ans << endl;
}