#!/usr/bin/env python3
N = int(input())
H = [int(x) for x in input().split()]

NH = [H[0]]
for h in H[1:]:
    if h != NH[-1]:
        NH.append(h)

while len(NH) < 3: NH.append(NH[-1])
H = NH
N = len(H)

ans = 0
for i in range(1, N-1):
    if H[i - 1] <= H[i] >= H[i + 1]: 
        l, r = i, i
        while 0 <= l - 1 and H[l - 1] <= H[l]: l = l - 1
        while r + 1 < N and H[r] >= H[r + 1]: r = r + 1
        ans = max(ans, min(H[i] - H[l], H[i] - H[r]))
print(ans)