#include <bits/stdc++.h>
using namespace std;
#define loop(i,b,e) for(int i=b;i<=e;i++)
#define loop2(i,e,b) for(int i=e;i>=b;i--)
#define io ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define fi first
#define se second
typedef long long ll;
typedef unsigned long long ull;
const int N = 1e6 + 5;
const ll mod = 1e9 + 7;
const int oo = 1e9;

int n;
ll t[N];

int main() {
    scanf("%d", &n);
    loop(i, 0, n - 1)
        cin >> t[i];
    if (t[1] - t[0] > t[n - 1] - t[n - 2]) {
        t[0] = 1e18;
    }
    else t[n-1] = 1e18;
    sort(t,t+n);
    ll mx = -1;
    int j = 0;
    loop(i, 1, n - 2) {
        if (t[i] - t[i - 1] > mx) {
            j = i;
            mx = t[i] - t[i - 1];
        }
    }
    t[n-1] = (t[j] + t[j - 1]) / 2;
    sort(t,t+n);
    ll ans = -1;
    loop(i, 1, n - 1)
        ans = max(ans,t[i]-t[i-1]);
    cout << ans;
}