---

package main

import (
	"fmt"
)

func Max(a int, b int) int {
	if a <= b {
		return b
	}
	return a
}

func main() {
	var n int
	fmt.Scanf("%d", &n)

	val := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scanf("%d", &val[i])
	}

	dp := make([][]int, n)
	for i := 0; i < n; i++ {
		dp[i] = make([]int, 4)
	}

	dp[0][0] = -val[0]
	dp[0][1] = 0
	dp[0][2] = -val[0]
	dp[0][3] = 0

	for i := 1; i < n; i++ {
		dp[i][0] = Max(dp[i - 1][0], -val[i])
		dp[i][1] = Max(dp[i - 1][1], dp[i][0] + val[i])
		dp[i][2] = Max(dp[i - 1][2], dp[i][1] - val[i])
		dp[i][3] = Max(dp[i - 1][3], dp[i][2] + val[i])
	}

	fmt.Println(dp[n - 1][3])
}