n = int(input('請輸入個數(shù)：'))
ls = input('請輸入數(shù)字：').split()
def solution(nums,n):
    if n==0 or n==1:
        return None
    elif n==2:
        return int(nums[1])-int(nums[0])
    else:
        max = int(nums[1])-int(nums[0])
        fast=2
        low=1
        while n>fast:
            temp = int(nums[fast])-int(nums[low])
            if max < temp:
                max = temp
                fast += 1
                low += 1
            else:
                fast += 1
                low += 1
                continue
        return max
res=solution(ls,n)
print(res)