import java.io.*;
import java.util.*;

public class motorway_mb {
    public static void main(String[] args) throws IOException {
        Input in = new Input();
        int n = in.nextInt();
        int[] s = new int[n];
        for (int i = 0; i < n; ++i) {
            s[i] = in.nextInt();
        }
        int[] suffixMax = new int[n];
        for (int i = n - 2; i >= 0; --i) {
            suffixMax[i] = Math.max(suffixMax[i + 1], s[i + 1] - s[i]);
        }
        int answer = Integer.MAX_VALUE;
        int prefixMax = 0;
        for (int i = 1; i + 1 < n; ++i) {
            answer = Math.min(answer, Math.max(s[i + 1] - s[i - 1], Math.max(prefixMax, suffixMax[i + 1])));
            prefixMax = Math.max(prefixMax, s[i] - s[i - 1]);
        }
        System.out.println(answer);
    }

    private static class Input {
        byte[] buf = new byte[2048];
        int curr, size;

        char next() throws IOException {
            if (curr == size) {
                curr = 0;
                size = System.in.read(buf);
            }
            char rv = (char) buf[curr];
            ++curr;
            return rv;
        }

        int nextInt() throws IOException {
            char ch;
            while ((ch = next()) <= ' ');
            int rv = ch - '0';
            while ((ch = next()) > ' ') {
                rv = 10 * rv + (ch - '0');
            }
            return rv;
        }
    }
}