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

peak = [False]*N
for i in range(1, N-1):
    if H[i] >= H[i-1] and H[i] >= H[i+1]:
        peak[i] = True
        peak[i-1] = False

ans = 0
for i in range(1, N-1):
    if peak[i]:
        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, H[i] - H[l])
print(ans)