//package misc.ukiepc2025

fun main() {
	readln()
	val a = readInts().zipWithNext { a, b -> b - a }
	val maxLeft = a.scan(0, ::maxOf)
	val maxRight = a.reversed().scan(0, ::maxOf).reversed()
	val ans = (0..a.size - 2).minOf { i ->
		maxOf(maxLeft[i], a[i] + a[i + 1], maxRight[i + 2])
	}
	println(ans)
}

private fun readStrings() = readln().split(" ")
private fun readInts() = readStrings().map { it.toInt() }