#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>

using namespace std;

int main()
{
    int n; cin >> n;
    vector<int> ve(n);
    for (int i = 0; i < n; ++i) cin >> ve[i];
    sort(ve.begin(), ve.end());
    ve.resize(unique(ve.begin(), ve.end()) - ve.begin());
    n = ve.size();
    vector<pair<int,int> > ans(n, { -1, -1 });
    ans[0].first = 0;
    for (int i = 1; i < n; ++i) {
        ans[i].first = max(ve[i] - ve[i - 1], ans[i - 1].first + 1);
    }
    ans.back().second = 0;
    for (int i = n - 2; i >= 0; --i) {
        ans[i].second = max(ve[i + 1] - ve[i], ans[i + 1].second + 1);
    }
    double res = (ve.back() - ve.front()) / 2.0;
    for (int i = 0; i < n; ++i) {
        double l = ans[i].first + 1, r = 1e9 + 4;
        for (int q = 0; q < 60; ++q) {
            double m = (l + r) / 2;
            int rp = upper_bound(ve.begin(), ve.end(), ve[i] + 2 * m) - ve.begin() - 1;
            if (ans[rp].second + 1 <= m) {
                r = m;
            }
            else {
                l = m;
            }
        }
        res = min(l, res);
    }
    cout << fixed << setprecision(1) << res;
    return 0;
}