HackerRank "Flatland Space Stations"

#include <vector>
#include <iostream>
using namespace std;


int main(){
    int n;
    int m;
    cin >> n >> m;
    vector<int> c(m);    
    for(int c_i = 0;c_i < m;c_i++){
       cin >> c[c_i];
    }
    sort(c.begin(), c.end());
    int r = 0;
    for(int i =0; i < m - 1; i ++)
    {
        r = max(r, (c[i + 1] - c[i])/2);
    }
    r = max(r, c[0]);
    r = max(r, n - c.back() - 1);
    cout << r << endl;
    
    return 0;
}