#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     long long t, v;     cin >> t >> v;     long long a[t];     for (int i = 0; i < t; i++) cin >> a[i];     long long minx = 0;     sort(a, a + t);     for (int z = 0; z < t - 1; z++) {       minx = max(a[z + 1] - a[z], minx);     }     long long diff = max(a[0] - 0, v - a[t - 1]);     double re;     re = max(double(diff), double(minx) / 2.0);     cout << setprecision(10) << fixed << re;   }   