mod = 998244353
n = int(input())
a = list(map(int, input().split()))[::-1]
difmax = max(ai - aj for ai, aj in zip(a, a[1:]))
amax = a[0]
sa = [0] * (amax + 1)
for d in range(difmax, amax + 1):
    dp = [0] * n
    s = dp[0] = 1
    l = 0
    for i in range(1, n):
        while a[l] - a[i] > d:
            s -= dp[l]
            s %= mod
            l += 1
        dp[i-1] += s
        dp[i-1] %= mod
        s += s
        s %= mod
    sa[d] = sum(dp) % mod
ans = sa[0]
ans += sum(i * (sa[i] - sa[i-1]) for i in range(1, amax + 1))
ans %= mod
print(ans)